Congress is taking a cautious approach to the massive street protests sweeping Egypt – encouraging cries for reform, but wary that a more radical regime in Cairo could damage US interests, including the survival of Israel.

In a rare display of bipartisanship, both Democrats and Republicans have largely deferred to the White House’s balanced tone and handling of events, including avoiding calls for 30-year President Hosni Mubarak to step down.

But as protests intensified in the streets of a key US ally, some Democrats are breaking ranks, while Republicans are largely standing behind President Obama's position. Sen. John Kerry (D) of Massachusetts called on Mr. Mubarak to “step aside gracefully to make way for a new political structure,” including an interim government before a planned September presidential vote.

“For three decades, the United States pursued a Mubarak policy,” he said in an opinion essay in Tuesday's New York Times. “Now we must look beyond the Mubarak era and devise an Egyptian policy.”

On Monday, Sen. Bill Nelson (D) of Florida urged Mubarek to take himself out of presidential elections in September. “Mubarak must immediately open these elections to international observers and give his written assurance that his name won’t appear as a contender,” he wrote in an op-ed in The Hill. “I believe this could help quell the protests.”

By contrast, Republicans are signaling strong support for Mr. Obama’s calls for the Egyptian government to adopt reforms and avoid violence against protesters. “We ought to speak as one voice during this crisis,” said Senate Republican leader Mitch McConnell on NBC’s “Meet the Press” on Sunday. Speaker John Boehner told Fox News Sunday that reform was needed in Egypt. “We have one president and one secretary of state, McConnell added, at a press briefing on Tuesday. “We’re all watching with great interest….We hope by the end of the day we still have a strong ally.”

“Senate Democrats are getting ahead of the president, while Republicans are not,” said Don Stewart, a spokesman for Senator McConnell. “Gitmo notwithstanding, we’ve had pretty consistent comity with the White House on foreign policy.” At a weekly communications meeting on Monday, GOP leaders urged staff to close ranks and back President Obama.

At issue is not just support of the president but avoiding responsibility for moves that could be seen as undermining a key ally in the region. Congress spent at least a decade debating “Who Lost China?” after the communist takeover in 1949. Congress is reluctant to challenge the White House for ownership of policies that could produce an anti-American regime in Cairo.

“Support for Mubarak has been such a long-standing principle in American history, going back to President Reagan. It’s hard to see a fundamental partisan fault line on this issue,” says Michael O’Hanlon, senior foreign policy fellow at the Brookings Institution.

Politics aside, says Mr. O'Hanlon, "Congress has the luxury of critiquing in response to administrative moves – in a way that will be more easily forgotten if the critiques turn out to be wrong."

A strong theme emerging on Capitol Hill – consistent with the Obama administration’s response – is to call for guarantees that Egypt’s presidential elections will be fair and open. Sen. John McCain (R) of Arizona called on Mubarak to restore access to social networking sites, repeal the emergency law, and “open greater space for political parties to organize and compete peacefully for power,” including independent monitors in next fall’s presidential election.

“I strongly believe the Egyptian military has no role to play in resolving the current situation,” said Mr. McCain, the top Republican on the Senate Armed Services panel, in a statement.

But lawmakers are divided over how to avoid an outcome that could produce a more radical regime in Egypt, hostile to Israel.

Rep. Ileana Ros-Lehtinen (R) of Florida, who chairs the House Foreign Affairs Committee, said that only parties who support Israel should be allowed to compete in fall elections.

“The U.S. should learn from past mistakes and support a process which only includes candidates who meet basic standards for leaders of responsible nations – candidates who have publicly renounced terrorism, uphold the rule of law, recognize Egypt's international commitments including its nonproliferation obligations and its peace agreement with the Jewish state of Israel, and who ensure security and peace with its neighbors,” she said in a statement.

Reps. Gary Ackerman (D) of New York and Dennis Kucinich (D) of Ohio called for cutting off $1.5 billion in annual US aid to Egypt, unless Mr. Mubarak accepts a transitional government and steps down. Rep. Howard Berman (D) of California, the top Democrat on the Foreign Affairs panel, called for a “constructive dialogue” between the Egyptian government and opposition leaders, but balked at cutting off aid.

“So long as the Egyptian military plays a constructive role in bringing about a democratic transition, the United States should also remain committed to our ongoing assistance programs for Egypt, both military and civilian, “ he said in a statement on Jan. 31.

But many Senate Democrats Tuesday were holding back comment on events they said were so critical for American interests. “This is a really delicate situation, as it relates to the entire Middle East region, especially as so many Arab states are our allies,” said Sen. Claire McCaskill (D) of Missouri. “I don’t think many of us should say much until this thing has had a chance to work itself out.”