Egypt's crackdown strains military ties with US
The Pentagon relies heavily on Cairo to allow overflights and access to the Suez, but this marriage of convenience is sorely strained
Most nations, including many close allies of the United States, require as much as a week's notice before US warplanes are allowed to cross their territory.
Not Egypt, which offers near-automatic approval for such overflights, to resupply the war effort in Afghanistan or to carry out counterterrorism operations in the Middle East, Southwest Asia or the Horn of Africa. Losing that route could significantly increase flight times to the region.
US warships are also allowed to cut to the front of the queue through the Suez Canal in times of crisis. Without Egypt's co-operation, military missions could take days longer.
Those are some of the largely invisible ways the Egyptian military has assisted the United States as it pursues its interests across the region - and why the generals now in charge in Cairo are not without their own leverage in dealing with Washington in the aftermath of President Barack Obama's condemnation on Thursday of the military's bloody crackdown on supporters of the former president, Mohammed Mursi.
In his first overtly punitive step, Obama cancelled the Bright Star military exercise, the largest and most visible sign of co-operation between the armed forces of the two nations.
But given the growing violence in Egypt, it might have been impossible to guarantee the safety of the thousands of US troops scheduled to deploy for the war game, and the decision to call it off might have been the wise move regardless of the politics. For the Pentagon, other steps might be more difficult.
"We need them for the Suez Canal, we need them for the peace treaty with Israel, we need them for the overflights, and we need them for the continued fight against violent extremists who are as much of a threat to Egypt's transition to democracy as they are to American interests," said General James Mattis, who retired this year as head of the US Central Command.
While a cosy relationship with the Egyptian military might be preferable for the United States' interests to a radicalised, hostile government in Cairo, there is also a threshold of violence - still unknown - that, if passed, would make it impossible for the US Defence Department to continue its dealings there.
There have been instances when the United States restricted or even severed military-to-military relations with a useful ally, for periods both long and short, because of authoritarian practices, human-rights violations or security policies at odds with those of Washington. Among the examples are Indonesia, Pakistan and the Philippines.
In the meantime, Obama administration officials are taking a hard look at possible incentives and punishments that might compel the generals in Cairo to end the crackdown and open a dialogue on transition to democratic governance.
"The violence is intolerable, but clearly they feel the nation of Egypt is facing a sovereign, existential crisis," said one Obama administration official.
The risk is that the United States might be left standing by as its allies in the Egyptian military lose control of the crisis.
"Both sides have a strong interest in preserving it and will work to that end," said Robert Springborg, a professor at the Naval Postgraduate School in Monterey, California, and an expert on the Egyptian military.