The Obama administration attempted to sidestep questions over the legality of military aid to Egypt on Monday, claiming it was not in its "best interests" to decide yet whether the armed overthrow of the country's elected president amounted to a coup or not.

US law prevents any administration providing support to the leaders of a military coup, but the White House announced it will not suspend foreign aid to Egypt for now, pending further review of how army generals behaved both during and after the change of regime in Cairo.

"We have had a long relationship with Egypt and the Egyptian people and it would not be wise to abruptly change our assistance programme," said spokesman Jay Carney. "The smart policy is to review this matter."

"There is not a simple or easy answer here," he added. "It is in our interests to observe and engage."

Despite mounting pressure from congressional critics such as Senator John McCain, the White House also refused to put a timeline on its suspension of judgment over the legal status of the revolt.

The US spends $1.3bn on military aid to Egypt each year, and a further $250m in economic assistance – a factor which the administration hopes may act as a check on military leaders and encourage them to return power swiftly to an elected government.

But congressional hawks see the issue as more evidence that the White House is "behind the curve" on events in the Middle East.

"It is difficult for me to conclude that what happened was anything other than a coup in which the military played a decisive role," said McCain.

"I do not want to suspend our critical assistance to Egypt but I believe that is the right thing to do at this time," he said.

Though adamant it is not picking sides, the administration argues it takes more than elections to make a democratic government and believes ousted president Mohamed Morsi should have done more to respect the views of opposition groups since winning the first election following the revolution against President Mubarak.

"It is important to acknowledge that tens of millions of Egyptians have legitimate grievances with Morsi's undemocratic form of government and do not believe it is a coup," said Carney.

But the US has also been heavily criticised in the region for allegedly inciting recent violence by giving what is seen as tacit backing to the overthrow of Morsi.

At least 51 people were killed in Cairo on Monday when the Egyptian army opened fire on supporters of the toppled Islamist leader.

"The US remains deeply concerned by increasing violence and dangerous levels of political polarisation," insisted White House spokesman Carney.

"We condemn any violence or incitement to violence and we call on the military to exercise restraint. We also condemn the explicit calls to violence by the Muslim Brotherhood."

He also called on army leaders to stop arresting Muslim Brotherhood leaders and allow a free press to operate, but declined to comment on how the White House felt they had behaved so far.

"What is not helpful is to give hourly or daily grades [to the generals]," said Carney. "We are making our broad position to clear to them."