U.S. officials expressed increasing pessimism Wednesday that Egyptian President Hosni Mubarak would be able serve out the remainder of his term.
Mubarak "obviously ... is not going to last until the election," a senior U.S. official told NBC News.
"This is a train out of control now," the official said, adding that "there is nothing we can do now, other than to wait for it and respond appropriately."
Sen. John McCain, who met with President Barack Obama earlier Wednesday, was more blunt.
"The rapidly deteriorating situation in Egypt leads me to the conclusion that President Mubarak needs to step down and relinquish power," McCain said. "It is clear that the only institution in Egypt that can restore order is the army, but I fear that for it to do so on behalf of a government led by or involving President Mubarak would only escalate the violence and compromise the army's legitimacy.
"I urge President Mubarak to transfer power to a caretaker administration that includes members of Egypt's military, government, civil society, and pro-democracy opposition, which can lead the country to free, fair, and internationally credible elections this year as part of a real transition to democracy," McCain added.
Mubarak, in a televised speech on Egyptian state TV, on Tuesday night announced he would not seek a sixth term when his current one expires in September. He earlier announced other moves, including the naming of a vice president, in a bid to pacify critics but rejected protesters' calls that he step down immediately.
The senior U.S. official, who spoke on the condition of anonymity, said: "The greatest contribution that President Mubarak can make to the cause of democracy in his country is to remove himself from power."
"The best-case scenario is that the protests settle down and the Mubarak transition is accelerated," the official said, and then the world can "begin to see some formation of what the interim government is going to look like before they even get to new leadership."
At his daily briefing Wednesday, State Department spokesperson P.J. Crowley spoke about the pressing need for a transition, saying that "the violence today just underscores how urgent the situation is. The longer that this goes unresolved, the greater the danger of further violence."
Asked whether the U.S. would like to see the elections in Egypt accelerated, Crowley said, "We want to see free, fair and credible elections. The sooner that can happen, the better."
White House spokesman Robert Gibbs echoed Obama's public call one night earlier for an immediate and orderly transition to democracy in Egypt. Instead the images on TV were of a brutal clash between protesters and Mubarak supporters.
"If any of the violence is instigated by the government, it should stop immediately," Gibbs said, while declining to speculate whether the Egyptian government was in fact behind the violence.
Obama has spelled out what Egypt's transition to free elections should look like, but he has refused to publicly say whether Mubarak should be in charge all the while. Obama has spoken to Mubarak and telephoned world leaders to try to bolster stability in the region, but he cannot stop violence in the streets of Cairo.
An Egyptian official, speaking for Mubarak's government, complained that the U.S. is pressing for Mubarak's swift departure even as the White House publicly urges an orderly transition.
The official, speaking from a location outside Egypt, told The Associated Press that Mubarak's decision not to seek re-election in September was not a result of pressure from Obama, who has spoken with the Egyptian leader twice since the street uprising began more than a week ago.
The official said in a statement: "There is a clear contradiction between an orderly process of transition and the insistence that this process be rushed."
The official spoke on condition of anonymity, saying his government would not allow him to associate his name with the statement.
He said Mubarak, in addition to agreeing not to run again, had appointed a vice president, stated his readiness for dialogue with the opposition and promised changes in the constitution.
"All of those things can't be done if there is a vacuum at the top," the official said.