WASHINGTON — The Obama administration is discussing with Egyptian officials a proposal for President Hosni Mubarak to resign immediately, turning over power to a transitional government headed by Vice President Omar Suleiman with the support of the Egyptian military, administration officials and Arab diplomats said Thursday.

Even though Mr. Mubarak has balked, so far, at leaving now, officials from both governments are continuing talks about a plan in which Mr. Suleiman, backed by Lt. Gen. Sami Enan, chief of the Egyptian armed forces, and Field Marshal Mohamed Tantawi, the defense minister, would immediately begin a process of constitutional reform.

The proposal also calls for the transitional government to invite members from a broad range of opposition groups, including the banned Muslim Brotherhood, to begin work to open up the country’s electoral system in an effort to bring about free and fair elections in September, the officials said.

Senior administration officials said that the proposal was one of several options under discussion with high-level Egyptian officials around Mr. Mubarak in an effort to persuade the president to step down now.

They cautioned that the outcome depended on several factors, not least Egypt’s own constitutional protocols and the mood of the protesters on the streets of Cairo and other Egyptian cities.

Some officials said there was not yet any indication that either Mr. Suleiman or the Egyptian military was willing to abandon Mr. Mubarak.

Even as the Obama administration is coalescing around a Mubarak-must-go-now posture in private conversations with Egyptian officials, Mr. Mubarak himself remains determined to stay until the election in September, American and Egyptian officials said. His backers forcibly pushed back on Thursday against what they viewed as American interference in Egypt’s internal affairs.

“What they’re asking cannot be done,” one senior Egyptian official said, citing clauses in the Egyptian Constitution that bar the vice president from assuming power. Under the Constitution, the speaker of Parliament would succeed the president. “That’s my technical answer,” the official added. “My political answer is they should mind their own business.”

Mr. Mubarak’s insistence on staying will again be tested by large street protests on Friday, which the demonstrators are calling his “day of departure,” when they plan to march on the presidential palace. The military’s pledge not to fire on the Egyptian people will be tested as well.

The discussions about finding a way out of the crisis in Cairo take place as new questions are being raised about whether American intelligence agencies, after the collapse of the Tunisian government, adequately warned the White House and top lawmakers about the prospects of an uprising in Egypt.

During a Senate hearing on Thursday, both Democrats and Republicans pressed a senior Central Intelligence Agency official about when the C.I.A. and other agencies notified President Obama of the looming crisis, and whether intelligence officers even monitored social networking sites and Internet forums to gauge popular sentiment in Egypt.

“At some point it had to have been obvious that there was going to be a huge demonstration,” said Senator Dianne Feinstein, the California Democrat who is chairwoman of the Senate’s Select Committee on Intelligence.

She said that intelligence agencies never sent a notice to her committee about the growing uprising in Egypt, as is customary in the case of significant global events.

Stephanie O’Sullivan, the C.I.A. official, responded that the agency had been tracking instability in Egypt for some time and had concluded that the government in Cairo was in an “untenable” situation. But, Ms. O’Sullivan said, “we didn’t know what the triggering mechanism would be.”

Because of the fervor now unleashed in Egypt, one Obama administration official said, Mr. Mubarak’s close aides expressed concern that they were not convinced that Mr. Mubarak’s resignation would satisfy the protesters.

In an interview with Christiane Amanpour of ABC News, Mr. Mubarak said that he was “fed up” with being president but that he could not step down for fear of sowing chaos in the country.

“The worry on Mubarak’s part is that if he says yes to this, there will be more demands,” said Leslie H. Gelb, president emeritus of the Council on Foreign Relations. “And since he’s not dealing with a legal entity, but a mob, how does he know there won’t be more demands tomorrow?”

A number of high-level American officials have reached out to the Egyptians in recent days. While administration officials would not offer details of the alternatives that were being discussed, they made it clear that their preferred outcome would be for Mr. Suleiman to take power as a transitional figure.

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