The European Union is taking "all necessary precautions" after the United States said it would close some embassies on Sunday because of security concerns, a spokesman said.

The U.S. issued a worldwide travel alert on Friday warning Americans that Al-Qaida may be planning attacks in August, particularly in the Middle East and North Africa.

The State Department travel alert was based on the same intelligence that prompted it to close 21 U.S. embassies and consulates this Sunday, chiefly those in the Muslim world, a U.S. official told Reuters on condition of anonymity.

"We are aware of the move by the U.S. and we are in contact with our U.S. counterparts," European Commission spokesman Alexandre Polack said. "Delegations of the EU in the affected region are liaising with U.S. embassies."

The EU had no immediate comment on an announcement by the U.S. government that it was issuing a worldwide travel alert, warning U.S. citizens about the "continued potential for terrorist attacks, particularly in the Middle East and North Africa."

The State Department said on Thursday that American embassies that would normally be open this Sunday - including those in Abu Dhabi, Baghdad and Cairo - would be closed that day because of the unspecified security concerns.

The chairman of the House of Representatives Foreign Affairs Committee, Ed Royce, said on Friday al Qaeda appeared to be linked to the threat that prompted the closure of the embassies.

At this stage, Polack said, the EU had no evidence of any threats that specifically concerned EU overseas delegations "but we are taking all necessary precautions." He gave no details.

Another EU official said he was not aware of any plans to close EU delegations on Sunday.

The EU's diplomatic service has 3,400 staff and 139 delegations around the world