The GuardianLeading opposition groups in Egypt, including the Muslim Brotherhood, are standing by a demand that President Hosni Mubarak resign before there can be a political agreement to end two weeks of mass protests against his regime.Pro-democracy campaigners called another mass demonstration for Tuesday to keep up the pressure on Mubarak to quit in the face of the government's attempts to marginalise the street protests as no longer relevant because political talks are under way.In Washington, Barack Obama expressed optimism about developments in Egypt. "Obviously Egypt has to negotiate a path, and I think they're making progress," he said.But there remains considerable suspicion within the opposition about the intentions of Mubarak's vice-president, Omar Suleiman, who is overseeing the political transition and leading the negotiations, particularly after the continued arrest of opposition activists and fresh harassment of the press.Mubarak's new cabinet, installed after he sacked the previous one in an attempt to placate protesters, held its first meeting today and promptly announced a 15% pay rise for government employees in an apparent attempt to buy support among workers hit by sharply rising food prices.The government also promised investigations into official corruption and widespread fraud that delivered the ruling party its large victory in last year's parliamentary election. The curfew was relaxed by an hour.But the government's attempts to return Egypt to normality with a call for a return to work and an end to the demonstrations met with only partial success. Banks opened for a second day but the stock exchange, which the government hoped would be trading, remained closed, as did schools and many businesses. The value of the Egyptian pound fell sharply.Suleiman met major opposition groups, including the outlawed Muslim Brotherhood, yesterday and made a series of concessions in the hope of defusing the protests. But Muslim Brotherhood members who attended the meeting said today that they "will continue in dialogue only if people's demands are respected".The Islamist group said this required "the immediate resignation of President Mubarak" as well as the dissolving of parliament, the release of political prisoners and the lifting of oppressive emergency laws.Other opposition leaders, including Mohamed ElBaradei, were sensitive to not being used to undermine the street protests and also said that Mubarak must quit for political change to take place. The leftwing Nasserist party has pulled out of talks until the president resigns. Mubarak has said he intends to remain in office until elections in September.Groups representing demonstrators across Egypt have said they will not end the protests until Mubarak has gone. They also want to see parliament dissolved and the lifting of the oppressive state of emergency among other measures.In Tahrir square, Cairo, tens of thousands of demonstrators turned out again today despite the government's attempts to marginalise the protesters by suggesting that with political negotiations underway, they are no longer relevant. The military has said it is under orders to reopen the road through the square, a move that would greatly weaken the demonstrations. Protesters sought to prevent any surprise assault by sleeping inside the tracks of the army's tanks and armoured vehicles.Unable