Egyptian troops, light tanks, armored vehicles and attack helicopters poured into the Sinai desert to root out increasingly aggressive Islamic militants in the most significant easing to date of a key provision in the landmark 1979 peace treaty with Israel: The demilitarization of the peninsula.

For more than 30 years, Egyptian soldiers with heavy weapons were virtually banned from much of Sinai to create a buffer between the longtime enemies. Now, Israel has green-lighted the surge in hopes militants on its doorstep will be defeated.

On Thursday, Israel's Political-Security Cabinet approved Egypt's request to deploy attack helicopters in the peninsula in efforts to combat the rampant terror cells based in Sinai. The authorization to deploy five helicopters will expire within a few days, but a senior official told Israel Radio that Egypt was closely coordinating its maneuvers in Sinai with Israel and that enforcing law and order there was a shared interest.

According to Israel Radio, the authorization had to be granted by the entire Cabinet, and was collected by phone from the individual ministers.

But talk of renegotiating the historic peace treaty is so far just talk. The reason may lie in the delicate realities of the new Egypt, where the fiercely anti-Israel Muslim Brotherhood has risen to political power — with one of its own as Egypt's first president since the ouster of Hosni Mubarak last year. The Islamist group has said that Egypt will continue to abide by the peace accord. At the same time, it has repeatedly called for changes in the treaty's limits on troops in Sinai, seen as humiliating.

But its calls may be mainly rhetoric for an Egyptian public among which anti-Israel feeling is high and amending the deal is popular.

Actually renegotiating the accord would require diplomatic gymnastics for the Brotherhood to keep its vow never to meet with Israeli officials. And any deal could be spun as the Brotherhood signing a peace agreement with its nemesis, no matter how much technical deniability the group tries to maintain.

Israel is willing to bend troop limits. But it is tepid to formal amendments for fear of enshrining too much firepower on its border, especially when Egypt's post-Mubarak future remains unclear.

A senior Israeli official told The Associated Press in Jerusalem that the question of amending the treaty has not been raised by the Egyptians so far, or by the Israelis. The official spoke on condition of anonymity because he was not authorized to speak to the media.

"No one is talking about changing the treaty," said Israeli lawmaker and former defense minister Binyamin Ben-Eliezer.

Asked about calls to amend the deal, the spokesman for Egyptian President Mohammed Morsi, of the Brotherhood, avoided a direct response. "The state respects international accords but at the same time serves the interest of the nation and Egyptian citizens," Yasser Ali told reporters Tuesday.

The new Sinai offensive was sparked by a stunning surprise attack Sunday by militants who killed 16 Egyptian soldiers in Sinai near the border with Gaza and Israel. The terrorists commandeered two Egyptian vehicles and charged toward the border with Israel, with one of the two vehicles penetrating Israeli territory only to be destroyed by Israeli fire moments later.

The attack has underlined how much security cooperation still continues between Egypt and Israel despite the Brotherhood's new prominence. Morsi may be president, but Mubarak-era military generals long accustomed to dealing with Israel still hold dominant authorities over him.

Middle-ranking security officials from the two nations communicate regularly. Cairo airport officials say hardly a week goes by without the arrival of a private plane of Israeli security officials who get whisked away from the tarmac for talks with their Egyptian counterparts and fly home hours later.

The 1979 peace deal won Egypt the return of the Sinai Peninsula, captured by Israel in the 1967 war. But it restricted the numbers of troops and types of weapons Egypt could station there. Nothing more than a light weapon was allowed in most of the peninsula. Only police, no soldiers, were allowed in the zone directly on the border.

That has been altered twice since. After it pulled out from the Mediterranean coastal Gaza Strip in 2005, Israel allowed Egypt to deploy 750 military border guards.

Last year, the lawlessness in Sinai after Mubarak's ouster prompted the Israelis to allow the deployment of some 3,500 troops with armored vehicles in the border zone.

Some estimates by Israel say Egypt deployed no more than 40-50 percent of the 3,500 troops. Egyptian officials have refused to comment on the number of troops.

Now Egypt is moving in more soldiers and sharply hiking its firepower after last weekend's attack. After intensive contacts between Egyptian and Israeli officials, Egypt early in the week sent at least two attack helicopters, 20 armored vehicles laden with an unspecified number of troops and elite counterterrorism policemen to the border zone, security and military officials in the area said. The officials spoke on condition of anonymity because they were not authorized to talk about the movements.

Overnight Tuesday-Wednesday, attack helicopters carried out their first strikes in the peninsula. On Thursday, 60 more vehicles, including 40 light tanks, complete with their crews, headed to the border region.

According to an Israel Radio report on Friday morning, around 60 terrorists have been killed so far in clashes with Egyptian troops in Sinai.

Sunday's attack was an alarm bell over the increasing boldness of Islamic terrorists in Sinai. It was at least the third attack into Israel by terrorists from Sinai since early 2011. Terrorists have also repeatedly attacked Egyptian army and security forces positions in northern Sinai, killing at least 50. Various terrorist groups, some with links to al-Qaida-inspired groups in Gaza, have cropped up, calling for an Islamic state in Egypt.

Terrorist activity in Sinai has grown for several years, fueled in part by resentment among many native Bedouins over police heavy-handedness and lack of adequate government services.

Things rapidly worsened after Mubarak's ouster. Police largely melted away and are still too afraid to patrol many areas. A massive flow of smuggled arms from Libya, including heavy machine guns, RPGs and anti-aircraft guns, is making its way to Sinai terrorists.

The crisis has been left to fester in the 18 months since Mubarak's fall while the military rulers who took power after him were tied down in political wrangling with the Brotherhood and other Egyptian factions.

"The military has been consumed by the political struggle that continues and issues of governance have not received diligent attention, Sinai included," said Michael W. Hanna of the Century Foundation in New York. "This negligence has been exacerbated by the overall deterioration of security in the post-Mubarak period."

Israel has been urging Egypt to go after terrorists. But its attitude has been that Egypt can do that with expanded troop limits, without amending the treaty.

"There are things that can be done ... to add (Egyptian) border forces of a higher quality in terms of weaponry, perhaps free movement of helicopters in certain areas, but not much more than that," said Eli Shaked, a former Israeli ambassador to Egypt.

"Israel sees Sinai as a strategic buffer zone of paramount importance. It should never be a springboard to launch any attack against Israel," he told the AP.

Israel remains the archenemy in the eyes of most Egyptians, and many dislike the treaty. Still, Mubarak was a reliable ally, building close security cooperation and economic ties with Israel during his 29 year rule.

The treaty, negotiated under U.S. sponsorship, has been diligently observed by both governments for 33 years. It successfully ended a state of war between the most powerful Arab nation and Israel after four ruinous wars. It also changed the geopolitical landscape of the Middle East.

But the threats have changed, as Sunday's attack made clear, said Nimrod Novik, who advised Israeli President Shimon Peres when he was prime minister and foreign minister. Novik advocates amending the treaty's military annex to let in Egyptian troops more suited to fighting militants, such as airborne paratroopers.

Moreover, if amended by mutual consent, Novik explained, it would amount to an endorsement of peace by what he called the "new Egypt" — a reference to its Islamist leaders.

"Since the peace treaty is a paramount strategic asset for Israel, this symbolic act is significant, too."

Defense Minister Ehud Barak says he does not doubt Egypt's ability to clean up Sinai, but was not so certain about its political will to do so.

"Time will tell," he told Israel Radio, but added: "We see operations we didn't see in the past. They are acting with a sweep and resolve I don't remember in the past."

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