The Muslim Brotherhood has warned that Egypt may review its 1979 peace deal with Israel if the United States cuts aid to the country, a move that could undermine a cornerstone of Washington's Middle East policy.

Washington has said the aid is at risk due to an Egyptian probe into civil society groups which has resulted in charges against at least 43 activists, including 19 Americans who have been banned from leaving the country.

Egypt has been one of the world's largest recipients of US aid since it signed the peace treaty with Israel, and the Brotherhood, which does not yet hold the reins of power, said any decision to cut that aid because of the investigation would raise serious questions.

"We (Egypt) are a party (to the treaty) and we will be harmed so it is our right to review the matter," Essam El-Erian, a senior Brotherhood leader, told Reuters in a telephone interview. Essam El-Erian is the head of the foreign affairs committee in the People's Assembly .

"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," added Erian, the deputy leader of the Brotherhood's Freedom and Justice Party, the biggest group in the newly elected parliament.

His remarks are likely to increase pressure on all sides to resolve one of the worst crises in US-Egyptian ties since the treaty was signed.

The 1979 treaty made Egypt the first Arab state to forge peace with Israel and underpinned Washington's relationship with Cairo during Hosni Mubarak's 30-year rule, during which the Brotherhood was officially banned.

The Sinai peninsula, captured by Israel in the 1967 Middle East war, was handed back to Egypt under the agreement, and diplomatic relations between Israel and Egypt were established.

The Brotherhood has emerged as the single biggest political force in Egypt since Mubarak was ousted a year ago, winning more than 43 percent of the seats in recent parliamentary elections.

But for now Egypt is ruled by a council of military generals that took power after Mubarak was forced to step down on 11 February, 2011. They are due to make way for an elected civilian president at the end of June.

The military council has repeatedly pledged to honour Egypt's international obligations, including the peace deal with Israel, a position the Brotherhood has shared until now.

But Erian's remarks suggested that US threats around the inquiry into non-governmental organisations (NGOs) had prompted the Brotherhood to start reconsidering its original position.

In his annual budget message to Congress this week, US President Barack Obama asked for military aid to Egypt to be kept at $1.3 billion and sought $250 million in economic aid.

But General Martin Dempsey, the chairman of the Joint Chiefs of Staff, said on Tuesday he had told Egypt's ruling generals that the NGO issue must be resolved satisfactorily to allow military cooperation with Cairo to continue.

A State Department spokeswoman also said that failure to resolve the impasse could endanger the funds.