CAIRO — The Islamist party that leads the new Egyptian Parliament is threatening to review the 1979 peace treaty with Israel if the United States cuts off aid to the country over a crackdown on American-backed nonprofit groups here.

The pact is considered a linchpin of regional stability, and the statements, from at least two senior leaders of the party, the political arm of the Muslim Brotherhood, represent the first time that Egyptians have explicitly raised it during an escalating standoff over the crackdown.

The Obama administration and Congressional leaders have already warned Egypt that the United States might cut off its annual aid to the country, which in the most recent budget came to $1.3 billion in military supplies and about $250 million in other subsidies, including some money directed to the nonprofit groups under investigation. At least two senators have introduced legislation that could curtail the aid, and the Brotherhood released its statements on Thursday as the House Foreign Affairs Committee held a hearing on the matter.

Leaders of the Brotherhood have said that they would respect the American-brokered 1979 treaty, and the seriousness of their new threats is hard to assess. Many analysts, as well as some Brotherhood leaders here, have cited internal domestic reasons to respect the treaty, mainly because it ensures peaceful borders at a time when Egypt can ill afford the cost of a military buildup and its economy teeters on the brink of collapse.

But at the same time, Egyptians have long considered American aid as a kind of payment for preserving the peace despite the popular resentment of Israel over its policies toward the Palestinians, widely seen here as a violation of the treaty.

In the clearest of multiple Brotherhood statements on the subject, Essam el-Erian, who is chairman of Parliament’s foreign affairs committee, told Reuters that the aid was “one of the commitments of the parties that signed the peace agreement, so if there is a breach from one side it gives the right of review to the parties.”

“We will be harmed,” he added, “so it is our right to review the matter.”

The crisis was set off by a criminal investigation into the foreign financing of nonprofit groups; the inquiry began last spring under the military council that took power after the ouster of President Hosni Mubarak. The council kept on the books severe restrictions on the operations and financing of nonprofit groups that made almost all the independent advocacy or rights groups operating in Egypt technically illegal.

Accompanied by repeated suggestions from government officials that “foreign hands” were stirring up street protests against military rule, the investigation has focused mainly on four organizations that receive American financing. Two, the International Republican Institute and the National Democratic Institute, were chartered to promote democracy and have close ties to Congressional party leaders. A third was Freedom House, which has a similar mandate. The fourth teaches journalism.

The investigation culminated in raids on the groups’ offices by squads of heavily armed riot police officers, the indictments of 16 Americans and 27 others, and a travel ban that has trapped at least a half-dozen Americans in Egypt.

The standoff poses a thorny political problem for the leaders of both countries. Washington would like to preserve its alliance with Egypt during this critical period but faces political pressure to secure the freedom of the Americans and to defend the nonprofit groups.

The United States is Egypt’s most important international benefactor, but it is also widely resented here for its support of Israel and the invasion of Iraq.

The Muslim Brotherhood, for its part, has appeared to seek the political middle ground, supporting a liberalization of the laws to allow nonprofit “civil society” groups to operate more freely while at the same time asserting that the United States cannot put itself above Egyptian laws.