Collisions between allies rarely come much bigger than the current spat between the US and Turkey: Ankara has recalled its ambassador to Washington, outraged at a vote in Congress declaring the massacres of Armenians by Ottoman Turks in 1915 to be genocide.

The vote, by the foreign affairs committee of the House of Representatives, has yet to go to a full vote and does not reflect the view of the Bush administration, which lobbied fiercely against it. Indeed, eight former secretaries of state signed a letter to Nancy Pelosi, the House speaker, warning of repercussions for US national security.