Washington (CNN) -- President Barack Obama and his administration "strongly condemn the outrageous and deplorable violence that's taken place on the streets of Cairo today" and want it to end quickly, White House Press Secretary Robert Gibbs said Wednesday.
Supporters of Egyptian President Hosni Mubarak attacked anti-government demonstrators in Cairo's Tahrir Square, and the ensuing violence killed three people and injured more than 600, according to Egypt's health minister.
"It is our hope that what we saw today we won't see tomorrow or Friday or into the weekend," Gibbs told reporters. "Obviously ... this is not all going to be wrapped up in a matter of hours. It's going to take some time."
Gibbs reiterated the Obama administration's opposition to any violence in the Egypt demonstrations, either by Egyptian security forces, protesters or criminal elements. He added that if the Egyptian government is instigating any of the violence, "it should stop immediately."
At the State Department, spokesman P.J. Crowley called the attacks by what he described as "thugs" a clear attempt to intimidate the anti-government protesters, who were demonstrating for a ninth straight day.
The United States doesn't know the identity of the "thugs," Crowley said, adding that others have identified them as "supporters of the government."
In an operation that started Monday, more than 1,900 U.S. citizens and their family members have been evacuated from Egypt, Crowley said, adding that further evacuations would take place Thursday.
The attacks came the day after Mubarak announced he would not seek re-election as part of a series of political reforms. Opposition activists and protesters, however, said Mubarak must step down immediately with a caretaker unity government running the country until elections for president and a new parliament can take place.
It was unclear whether such confrontations were being repeated elsewhere. Other Cairo neighborhoods were calm, and contesting rallies in Egypt's second largest city, Alexandria, were largely peaceful.
Gibbs said the time for a political transition in Egypt "is now" because the Egyptian people "need to see change," and a "meaningful transition must include opposition voices and parties being involved in this process as we move toward free and fair elections."
At the same time, Gibbs noted that events in Egypt "have moved enormously quickly in a very volatile region of the world," adding: "What we're watching is history being made."
High-level contacts between the U.S. and Egyptian governments continued Wednesday, with Secretary of State Hillary Clinton talking to newly appointed Egyptian Vice President Omar Suleiman, Crowley said. And Pentagon spokesman Geoff Morrell said Defense Secretary Robert Gates spoke by phone with Egypt's defense minister on Wednesday, their third conversation in recent days.
Those contacts followed separate meetings on Monday between former U.S. ambassador to Egypt Frank Wisner, who traveled to Cairo to deliver a message on behalf of Obama, with Mubarak and Suleiman, according to Crowley.
A senior State Department official said on condition of not being identified that Mubarak has "a narrow amount of time" to make changes or take steps, with more demonstrations planned for Friday. However, the official said "there is a sentiment in the (Egyptian) government they can outlive the protesters."
"This is a false assumption," the official said. "They are not going away."
Meanwhile, a senior U.S. official who spoke on condition of not being identified expressed concern that Mubarak loyalists might have unleashed pro-Mubarak forces to intimidate protesters.
The Obama administration believes Mubarak's inner circle is debating whether Mubarak needs to do more to meet protester demands, according to the senior U.S. official.
However, an Egyptian government official said on condition of not being identified that his government has a "serious problem" with how the Obama administration has been "spinning" the events to give the impression that Mubarak's statement Tuesday night resulted from pressure from Obama.
"This is Mubarak's decision," the Egyptian official said. "Clearly, yes, he has been listening to the messages coming from the administration ... but at the end of the day, this is a decision he had come to on his own in the interests of Egypt, first and foremost, and as he said, as a result of listening very carefully to the demands of the Egyptian people."
The Egyptian official said his government has rejected calls by Obama and other world leaders to begin the transition now.
"This is an Egyptian process," the official said. "What President Mubarak said is that his primary responsibility is to ensure security and order so as to ensure a peaceful transfer of power so that the Egyptian people may decide their next leader in the upcoming presidential elections."
The official noted that the steps announced by Mubarak included the resignation of the government, formation of a new cabinet, appointment of Suleiman as vice president, announcing he will not run again, planned changes to the constitution, opening a dialogue with the opposition and various issues involving last year's parliamentary elections.
CNN's Jill Dougherty, Elise Labott, Chris Lawrence and Tom Cohen contributed to this story.