Piers Morgan talks with former British Prime Minister Tony Blair about the crisis in Egypt. Then, Anderson Cooper reports live from Cairo with the latest on what's happening on the ground. Don't miss CNN prime time Tuesday with "Piers Morgan Tonight" at 9 p.m. ET and "AC360º" at 10 ET on CNN.
Washington (CNN) -- A U.S. envoy sent by President Barack Obama urged Egyptian President Hosni Mubarak to announce that he won't run for re-election later this year, sources told CNN on Tuesday.
The move signaled a major shift in U.S. foreign policy regarding Egypt, the main Arab ally of the United States and a vital partner in the Middle East peace process because of its 1978 treaty with Israel.
According to the sources, who spoke on condition of not being identified by name, former U.S. Ambassador to Egypt Frank Wisner conveyed the message to Mubarak in Egypt. It was unclear whether the meeting was Monday or Tuesday.
Facing growing street demonstrations calling for his ouster, Mubarak reportedly was set to address his nation later Tuesday.
Until now, the weeklong street demonstrations in Egypt demanding Mubarak's ouster had drawn a measured U.S. response that advocated step-by-step reforms for pro-democracy changes while maintaining stability.
This week, though, calls increased for the Obama administration to push for Mubarak to announce that he would not be a candidate in the next presidential election scheduled for September.
One of Egypt's leading opposition figures, Mohamed ElBaradei, warned Monday that the United States needs to "let go" of its longtime ally.
"You need to review your policy," ElBaradei, the former head of the International Atomic Energy Agency, told CNN's "Anderson Cooper 360" in an interview Monday night. "You need to let go of Mubarak. You shouldn't be behind the curve, and you need to start building confidence with the people and not with the people who are smothering the people."
The unrest in Egypt presented Obama with a complex issue that lacked easy answers.
Egypt, the main Arab ally of the United States, is inexorably linked to neighboring Israel, the main U.S. ally in the Middle East, by a peace treaty that guarantees more than $1 billion a year in U.S. military aid to Mubarak's government.
Egypt also provides vital logistical and intelligence assistance to the United States, which has urged Mubarak for years to implement democratic reforms but always put the strategic benefits first.
Daniel Kurtzer, the U.S. ambassador to Egypt from 1997 to 2001, said the administration wants to both support "an exceedingly strong ally" and promote democratic reform and more openness in "a closed authoritarian society."
"The United States is trying to find comfortable ground in which we can argue for both without abandoning an ally and without abandoning our principles," Kurtzer said Monday.
The unrest in Egypt follows years of social, political and economic grievances that fueled the street protests that began last week and have since escalated. After ruling with an iron fist for three decades, Mubarak has given no indication of giving up power.
Demonstrators in Egypt question why Obama, who championed human rights and democracy in a 2009 speech in Cairo, isn't condemning Mubarak and applying pressure to help bring the changes they seek.
ElBaradei, who returned to his native Egypt last week as an opposition figure, said Egyptians need to see that the United States is supporting their aspirations.
"People need to see that you not only talk the talk, but walk the walk, and people need to understand and believe that you really, seriously take democracy, rule of law, freedoms seriously," ElBaradei said Sunday. Asking "a dictator" to implement democratic reforms "is an oxymoron, frankly."
U.S. Secretary of State Hillary Clinton outlined the administration's stance in separate interviews Sunday with five television networks, saying the "complex, very difficult" situation in Egypt requires careful progress toward a peaceful transition to democracy rather than any sudden or violent change that could undermine the aspirations of the protesters.
On Monday, White House Press Secretary Robert Gibbs said Egypt's government should engage in "meaningful negotiations with a broad section of civil society, including opposition groups," and hold "free and fair elections" in September.
The transition called for by Clinton "means change, and what we've advocated from the very beginning is that the way Egypt looks and operates must change," Gibbs said.
At the same time, he said, it is not the place of the United States to support or oppose the possible ouster of Mubarak.
Allies concurred, with German Foreign Minister Guido Westerwelle calling Monday for future "free and fair elections" in Egypt.
"We are also interested in a stable situation in the Middle East because, of course, Egypt is a key player for the whole region," Westerwelle said.
Even administration critics such as conservative Republican Sen. John McCain of Arizona have backed the U.S. response.
"I hope we all understand how important Egypt is as an ally, as a center of culture," McCain said Sunday on CNN, later adding that "what we need to do now is to lay out a plan for Mubarak to lift the state of emergency, announce that elections -- free and fair -- will be held in September, which were already planned, allow an open and free democratic process -- which I think we could have some confidence (in) if it was an open process that you would see a free and fair election -- and that we make sure that the aspirations of the Egyptian people are realized finally."
But some U.S. politicians disagreed. Democratic Sen. Bill Nelson of Florida said Monday that "Mubarak will have to go -- but not without an exit strategy that prevents the government from falling and leaving the door open for extremists."
To Marina Ottaway, director of the Middle East program at the Carnegie Endowment for International Peace, the unrest in Egypt showed that the U.S. policy of backing Mubarak despite his poor record on political and human rights has failed to bring desired stability.
Instead of what she labeled "subtle" language such as endorsing an orderly transition, the United States should call for a government of national unity to take over until fully democratic elections for both the presidency and the parliament, Ottaway said Monday.
CNN's John King, Elise Labott and Tom Cohen contributed to this story.