This comes as Washington is continuing to evaluate last week's overthrow of President Mohammed Morsi by the army.

US massive military aid to Cairo would have to be cut by law if the removal of the Islamist leader is determined by Washington to have been a coup.

The Muslim Brotherhood, which backs Mr Morsi, is demanding his reinstatement.

Its supporters have been staging mass protests near Cairo's barracks, where he is believed to be being held. On Monday, more than 50 Brotherhood loyalists were killed in clashes with the army.

The US officials say Washington will deliver four F-16 fighter jets in the next few weeks.

They are part of an already agreed bigger order of 20 planes - eight of which were sent to Egypt in January. The final eight are expected to be shipped later this year.

White House spokesman Jay Carney on Wednesday reiterated that it would not be "in the best interests of the United States to make immediate changes to our assistance programmes".

He added that the administration would take its time to consider the implications of removing Mr Morsi from power.

US military aid to Egypt is estimated to be $1.3bn (£860m) each year.

President Barack Obama has been careful not to use the word "coup" in relation to the recent events in Egypt to avoid triggering a legal cut-off of aid, the BBC's Katy Watson in Washington reports.

'Strong condemnation'

An Egyptian foreign ministry spokesman has said Mr Morsi is being held in a "safe place" and treated in a "very dignified manner".

Meanwhile, arrest warrants have been issued for the leader of the Muslim Brotherhood, Mohamed Badie, and nine senior figures.

They are charged with inciting Monday's deadly violence in the capital.

There are conflicting reports about what happened during the protest outside the Presidential Guard barracks, when more than 50 Brotherhood supporters were killed, as well as a soldier and two policemen.

The Brotherhood says the army fired on peaceful demonstrators and is accusing the interim authorities of a cover up. The military, however, say they acted in self-defence after being attack by armed assailants.

Many Brotherhood members are already in detention and warrants are said to have been been issued for hundreds more.

The new arrest warrants could scupper any attempts to persuade the Brotherhood to participate in the transitional political process, analysts say.

There is a feeling among the protesters that they have returned to the situation they were in under former President Hosni Mubarak, when the movement was banned and its members hunted down, our correspondent adds.

The timetable for new elections, announced in a constitutional declaration by interim President Adly Mansour on Monday evening, laid out plans to set up a panel to amend the suspended constitution within 15 days.

The changes would then be put to a referendum - to be organised within four months - which would pave the way for parliamentary elections, possibly in early 2014.

Once the new parliament convenes, elections would be called to appoint a new president.

However, the Brotherhood's political wing, the Freedom and Justice Party, and main liberal National Salvation Front opposition coalition and the grassroots Tamarod protest movement have all rejected the transition plan.