The Obama administration today resisted calls to cut its massive military aid to Egypt and is instead working behind the scenes with the commanders of the country's armed forces on how to oust President Hosni Mubarak.

The White House sees the Egyptian military as the key to removing Mubarak, regarded as a necessary first step towards implementing substantive political and economic reforms. Cutting aid would risk alienating them.

The US defence secretary, Robert Gates, the chair of the joint chiefs of staff, Admiral Mike Mullen, and other senior Pentagon figures have been in regular contact with their Egyptian counterparts all week.

Mullen, in an interview with ABC television today, said the US should wait to see what happens next before suspending aid, which amounts to more than $1.3bn (£800m) a year.

"There is a lot of uncertainty out there and I would just caution against doing anything until we really understand what's going on," he said. "I recognise that [$1.3bn] certainly is a significant investment, but it's an investment that has paid off for a long, long time."

The US and Egyptian armies are closely intertwined, not just through military aid but joint training and exercises.

The US would suspend aid immediately if the military was to crackdown on peaceful protesters in the way of the Iranian Revolutionary Guard in 2009 and the Chinese military in 1989.

Mullen said he had been in contact with his counterpart in Egypt, who assured him the miliary would remain neutral and not fire on the protesters.

Haim Malka, deputy director of Washington's Centre for Strategic and International Studies, said suspending aid would be a mistake. "The United States's ability to influence that system is already limited. Freezing military aid now undermines what leverage the US government does have to promote a post-Mubarak system that is more than just a reconfiguration of the status quo," he said.

The Pentagon press spokesman, Geoff Morrell, said Gates had spoken with the Egyptian defence minister, Mohamed Hussein Tantawi, three times this week. Tantawi visited Tahrir Square today to talk with anti-government protesters, signalling that the military would not participate in a crackdown.

Mullen has been in contact with Lieutenant-General Sami Enan, a national hero in Egypt. Under one of the options being discussed between the US and the Egyptian military, Enan would lead the transitional process along with the new vice-president, Omar Suleiman, the former head of intelligence who is close to the military, as well as Tantawi.

The US vice-president, Joe Biden, spoke with Suleiman yesterday.

The White House has been criticised throughout the week for failing to call unambiguously for Mubarak to go immediately. But the administration does not want to alienate pro-American leaders in Saudi Arabia and elsewhere in the region with an unseemly rush to dump a long-time ally. It also does not want to be seen as interfering in Egyptian domestic politics and fears humiliating Mubarak would be counterproductive to efforts to push him towards the exit.

The Obama administration is keen for him to leave as soon as possible so the reform process can get under way that will hopefully lead to free and fair elections.

"The president has said that now is the time to begin a peaceful, orderly and meaningful transition, with credible, inclusive negotiations," a White House spokesman, Tommy Vietor, said. "We have discussed with the Egyptians a variety of different ways to move that process forward, but all of those decisions must be made by the Egyptian people."