The United States said on Friday it would work with other nations to resolve Egypt's crisis peacefully, injecting new energy into a push to end a bloody standoff since the overthrow of Islamist President Mohamed Morsi.

A day after saying the army had restored democracy by removing Mursi, U.S. Secretary of State John Kerry urged Egyptian authorities to give demonstrators the space to protest in peace - a warning against dispersing pro-Morsi sit-ins.

"Egypt needs to get back to a new normal, it needs to restore stability, to be able to attract business and put people to work," Kerry said before a meeting United Arab Emirates Foreign Minister Sheikh Abdullah bin Zayed in London.

"We will work very, very hard together with others, in order to bring parties together to find a peaceful resolution that grows the democracy and respects the rights of everybody."

This appeared to signal a new diplomatic effort to end the crisis in which more than 300 people have been killed since the army removed Mursi and his Muslim Brotherhood from power on July 3 in response to mass protests against his rule.

Analysts say civilian members of the army-backed interim administration are trying to promote a political solution against the wishes of the security services which want to crack down hard on the Brotherhood.

Mohamed ElBaradei, vice president in the new administration, said he was lobbying for a peaceful outcome against others advocating crushing the Brotherhood.

"People are very angry with me because I am saying, 'Let's take time, let's talk to them'. The mood right now is, 'Let's crush them, let's not talk to them', said ElBaradei, pressing the Brotherhood to compromise. "I hope the Brotherhood understands that time is not on their side. I'm holding the fort, but I can't hold it for very long."

Egypt is more polarised than at any time since the downfall of autocratic president Hosni Mubarak in 2011, complicating mediation efforts in a pivotal Arab state fraught with unrest.

In a possible attempt to ease tensions, Egyptian state TV reported that the Interior Ministry did not want to break up Brotherhood protests in Cairo by force. It would, however, impose a cordon around them, the TV said, without saying when.

But trouble flared elsewhere in the Egyptian capital.

The Brotherhood, decrying what it sees as a coup against the country's first freely-elected head of state, announced two new sit-ins and its supporters clashed with police during a protest near a complex of television studios outside Cairo.

Tear gas was fired and state media reported army helicopters hovered overhead. The Brotherhood also announced marches to three sensitive security installations later on Friday, raising the prospect of more violence.

With the United States supplying Egypt with $1.3 billion in military aid each year and the United Arab Emirates having pledged $3 billion to the new administration, the countries may be able to help force a compromise.

In London, Sheikh Abdullah said a peaceful resolution required "inclusive dialogue". Qatar, which backed the Mursi administration with substantial financial aid, will help by liaising with the Brotherhood.

"The UAE, with the United States and others, is doing its very best to give this government the support it needs, but also to encourage all the other parties to reach a position where it can negotiate with this government - here I'm talking about the previous government," the Sheikh Abdullah said.

The army-backed government has drawn up a transition plan envisaging parliamentary and presidential elections that will start in about six months. But the Brotherhood protests are threatening to rob the government of a semblance of normality it needs to revive an economy which deep in crisis.

Morsi has been in detention since he was deposed and is facing a judicial inquiry into accusations of murder and conspiring with the Palestinian group Hamas.

Sisi need for political solution

The authorities have also rounded up many other Brotherhood leaders, feeding international fears of a plan to uproot a group that was suppressed for decades until Mubarak was ousted.

The Brotherhood leadership has mostly been accused of inciting violence. The government accuses Mursi's supporters of taking up arms, even alleging they engage in terrorism.

ElBaradei, a former United Nations nuclear chief, outlined ideas for a political deal that might include a pardon for Mursi and guarantees that the Brotherhood would have a place in political life. Speaking in an interview with the Washington Post, he said army chief Abdel Fattah al-Sisi understood the need for a political solution.

"But of course he has a responsibility to protect the country in terms of security. And the army is on the edge."

He said dialogue was the way to end the Brotherhood sit-ins. The government promised this week to break up the protests, describing them as a threat to national security. "I do not want to see any more bloodshed. Nobody wants that.

We are doing our best," ElBaradei said.

"They need to cooperate," he added, in reference to the Brotherhood. "But they need of course to feel secure, they need immunity, they need to feel that they are not excluded. It's things we are willing to provide."

He added that Sisi, who has gained enormous popularity since deposing Mursi, was not thinking of running for president.

The biggest sit-in is in northeast Cairo, where several thousand Mursi supporters have been camped out for more than a month in a protest that at times swells to tens of thousands.

The order to clear the protest raised fears of mass casualties after 80 of Mursi's supporters were shot dead by security forces last Saturday in violence near the sit-in.

But the authorities have so far held off, giving the diplomats more time to find a solution.

"The idea of storming the camp by force is one rejected by the Interior Ministry, but a blockade will be imposed in all the streets leading to Rabaa," state TV's security correspondent reported from outside the Interior Ministry. He was referring to Rabaa al-Adawiya, site of the biggest of sit-in.

'We're not terrorists'

"We are here with our wives and children. We don't want violence," said Ali el-Shishtawi, a government employee at the sit-in. "We're not afraid. We're not terrorists like they say."

The new government gained a U.S. seal of approval late on Thursday when Kerry said the army had been "restoring democracy" when it toppled Mursi - Washington's strongest endorsement yet for the new leadership.

"The military was asked to intervene by millions and millions of people, all of whom were afraid of a descent into chaos, into violence," Kerry told GEO TV in Pakistan. "And the military did not take over, to the best of our judgment - so far."

Washington's efforts to avoid calling Mursi's overthrow a "military coup" has left it open to charges of sending mixed messages about events in Egypt, long a bulwark of U.S. Middle East policy.

Mohamed Ali Bishr, a senior Brotherhood leader and a minister in Mursi's former government, said the movement was disappointed by Kerry's statement.

"The United States is a country that speaks of democracy and human rights and they say something like that. I hope that they rethink their position and correct it," he told Reuters.