The stand-off between Britain and Iran is not the only tension building in the Gulf this week.

Tensions are also building between the US and Saudi Arabia, reflecting growing differences between the two long-time allies as the Saudis take a greater leadership role in the region.

Saudi King Abdullah rattled Washington on Wednesday by telling an Arab summit that, “In beloved Iraq, blood flows between brothers in the shadow of illegitimate foreign occupation and hateful sectarianism, threatening a civil war.”

The US has now rejected Saudi Arabia’s charge that Iraq is under an “illegitimate foreign occupation” and said US. troops are there at Iraq’s invitation, under a U.N. mandate.  “When it comes to the coalition forces being in Iraq, we are there under the U.N. Security Council resolutions and at the invitation of the Iraqi people,” White House spokeswoman Dana Perino.