Egyptian troops, light tanks, armored vehicles and attack helicopters are pouring 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.

But talk of formally changing the treaty remains just that, 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 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 was not 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 Benjamin 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 that killed 16 Egyptian soldiers in Sinai near the border with Gaza and Israel.

It 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 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 troop numbers.

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.