Washington: As Egyptian President Hosni Mubarak stubbornly clung to power sparking more protests, US President Barack Obama mounted pressure on the embattled regime asking 'to move swiftly to explain the changes'.

Asserting that Mubarak has not convinced the Egyptian people that his handover of powers 'is immediate, meaningful or sufficient', he asked the Cairo regime 'to spell out in clear and unambiguous language' the process that will lead to democracy.

"The Egyptian people have been told that there was a transition of authority, but it is not yet clear that this transition is immediate, meaningful or sufficient," Obama said in a statement hours after Mubarak went on Egyptiam national TV to say he would reject international calls to resign.

Instead, Mubarak said he would hand over some powers to his vice president Omar Suleiman prompting demonstrators to take to the streets of Egypt's major cities to demand an end to Mubarak's 30-year rule, CNN reported from Cairo.

"Too many Egyptians remain unconvinced that the government is serious about a genuine transition to democracy, and it is the responsibility of the government to speak clearly to the Egyptian people and the world," Obama said.

"The Egyptian government must put forward a credible, concrete and unequivocal path toward genuine democracy, and they have not yet seized that opportunity."

Obama did not call on Mubarak to step down, but he did call for emergency law to be lifted while negotiations continue among the government, opposition parties and civil society on the country's future.

"As we have said from the beginning of this unrest, the future of Egypt will be determined by the Egyptian people. But the United States has also been clear that we stand for a set of core principles," he said.

"We believe that the universal rights of the Egyptian people must be respected, and their aspirations must be met," Obama said clearing siding with the demonstrators.

"We believe that this transition must immediately demonstrate irreversible political change, and a negotiated path to democracy."

Shortly after Mubarak spoke, Egypt's ambassador to the United States, Sameh Shoukry said: "The vice president is the de facto president."

Mubarak's refusal to step down apparently caught the Obama administration off-guard, going by Obama's remarks at Northern Michigan University in Marquette, Michigan earlier Thursday amid rumours that Mubarak was planning to step down.

"What is absolutely clear is that we are witnessing history unfold. It's a moment of transformation that's taking place because the people of Egypt are calling for change," he said.

"And they've turned out in extraordinary numbers representing all ages and all walks of life, but it's young people who've been at the forefront - a new generation, your generation, who want their voices to be heard.

"And so going forward, we want those young people and we want all Egyptians to know America will continue to do everything that we can to support an orderly and genuine transition to democracy in Egypt," Obama said.

Even CIA Director Leon Panetta testified before the House intelligence committee on Thursday that there was a 'strong likelihood' that Mubarak would step down by the end of the day.