ABU DHABI Ñ The United States and Britain have warned their nationals of an imminent attack in Kuwait.

The embassies of both NATO countries have put out an alert in Kuwait that Al Qaida-aligned insurgents were preparing an imminent strike in the sheikdom. The embassies called on their citizens to be vigilant and lower their profile.

The U.S. embassy urged Americans to immediately report any suspicious activity to the Kuwaiti police or the embassy. There are 12,500 U.S. nationals in Kuwait and another 25,000 U.S. soldiers, Middle East Newsline reported.

"The embassy is issuing this message because it has credible information that terrorist groups are developing near-term plans for attacks against unspecified targets in Kuwait," the U.S. embassy said in a Dec. 14 warden message. "The embassy reminds all U.S. citizens to exercise caution, maintain a low profile and avoid areas where Westerners are known to congregate."

"From time to time, the U.S. embassy in Kuwait may restrict the travel of official Americans or suspend public services for security reasons," the warden message added.

On Thursday, State Department spokesman Richard Boucher said the United States received an alert of an imminent attack on an unspecified target.

Boucher said the United States was working with Kuwait to foil any strike against the sheikdom.

"It's an unspecified target, so we can't tell," Boucher said. "But whenever we think somebody is preparing a terrorist attack, people need to be at a higher state of vigilance."

Later, the British embassy in Kuwait issued a similar warning. "There is a high threat from terrorism against Western, including British, interests," the British embassy said. "Attacks could be indiscriminate and against civilian targets, as they have been elsewhere in the region."

Kuwaiti officials said there has not been any new information of an imminent attack by Al Qaida or related groups. They said authorities have increased security around Western embassies and other installations.

Earlier, Kuwait bolstered security around oil and other key installations following an Al Qaida attack on the U.S. consulate in Jedda on Dec. 6. In July 2004, Kuwaiti authorities arrested Kuwaiti nationals suspected of planning Al Qaida-aligned strikes in the Gulf region.

The last reported attack on Americans in Kuwait was in December 2003. At the time, a U.S. military convoy came under fire outside Kuwait City, in which four American soldiers were injured.