The U.S. government expressed its grave concerns on Monday about what it considered as the Egyptian ruling military council's decisions to delay its power transfer to a civilian government following the presidential election.

"We're particularly concerned by decisions that appear to prolong the military's hold on power," State Department's spokeswoman Victoria Nuland told reporters at a news briefing.

The U.S. urged the Supreme Council of the Armed Forces (SCAF) in Egypt "to restore popular and international confidence in the democratic transition process by following through on their stated commitments to an inclusive constitutional drafting process, the timely seating of a democratically elected parliament, and the swift, permanent transfer of power to a civilian government," she added.

Nuland was making the comments on the just-concluded presidential election held Sunday in Egypt, which was won by Mohamed Morsi, a member of Egypt's Muslim Brotherhood, after defeating his rival and former premier Ahmed Shafiq.

The SCAF, which took over power in February 2011 after former president Hosni Mubarak was ousted amid mass protests, told a press conference in Cairo on Monday that it promised to transfer power to the elected president by the end of this month, the official Egyptian news agency MENA reported.

But the SCAF issued a supplementary constitutional declaration on Sunday night to retake legislative powers after the parliament was dissolved several days ago, a move seen by the U.S. as a bid by the Egyptian military to prolong its hold on power.

"What we want to see is a democratically elected president, a democratically elected parliament, a constitution that reflects the will of the Egyptian people, and a full transfer of power back to civilian rule as quickly as possible," Nuland said.

She said the U.S. stands with the Egyptian people in their aspiration to choose their own leaders, stressing that there "can be no going back on the democratic transition."

The U.S. Defense Department also expressed deep concerns on Monday about the SCAF's new amendments to Egypt's constitutional declaration and the timing of the announcement.

"We have, and will continue, to urge the SCAF to relinquish power to civilian-elected authorities and to respect the universal rights of the Egyptian people and the rule of law," Pentagon spokesman George Little told reporters.

Egypt's Supreme Constitutional Court voided the Islamists- dominated People's Assembly (lower house of parliament) last Thursday, citing the parliament election law was unconstitutional, but the Muslim Brotherhood rejected the decision to dissolve the parliament and called for a referendum on its fate.