The United States Embassy in Khartoum (search) will suspend normal operations beginning Wednesday as the result of terror threats to American interests in Sudan, the embassy said Monday.

A warden message was distributed to Americans living in Sudan, which does not have full diplomatic relations with the United States.

The embassy urged all Americans in the country in northeastern Africa to maintain a low profile, and to avoid large gatherings of foreigners, which may attract attention.

In the statement, the embassy said it was already closing Tuesday for the Veterans Day (search) holiday, and its operations would remain suspended for the rest of the week.

Sudan is on the U.S. State Department's list of State Sponsors of Terrorism.

The United States is cooperating with the government on counterterrorism, but concerns remain, particularly about the presence of Hamas and Palestinian Islamic Jihad, according to the State Department.

The U.S. withdrew its ambassador to Sudan in 1996 and has never sent one back, although a handful of embassy employees are still there.

A consular official visits periodically to handle visa requests for American citizens, but the official's ability to provide other consular services, including emergency assistance, is severely limited.

The embassy hopes to resume normal operations next week.

U.S. citizens who remain in or travel to Sudan despite the warning were encouraged to register with the U.S. Embassy in Khartoum and to obtain updated information on travel and security in Sudan.

The warning follows Saturday's car bombing attack in Riyadh (search), Saudi Arabia, which killed 17 people at a compound housing mostly Arab foreigners.

The U.S. Embassy there had closed its offices earlier that day to review security procedures after receiving credible information about planned terror attacks.

Restrictions on staff and families were slightly eased Monday, but security was tight elsewhere in Saudi Arabia, amid fears of more attacks. Officials have said the bombing bore similarities to previous Al Qaeda-suspected operations.

After a review of the threat level, U.S. Embassy staff and their families were told they could travel outside Riyadh's heavily guarded diplomatic quarter, to which they had been restricted since the attack, an embassy spokeswoman said.

The embassy is shut indefinitely. The State Department has made no decision to evacuate diplomats or dependents.

Saudi authorities, who have clashed recently with suspected Al Qaeda militants, said earlier this month they were increasing security in the holy city of Mecca. Security officials were particularly concerned about the last 10 days of the fasting month of Ramadan, when some 2 million Muslims are expected to perform the "omra," or minor pilgrimage, to Mecca. Ramadan ends around Nov. 24.

After a Nov. 3 shootout in Mecca that left two suspects dead, Saudi authorities confiscated a large cache of weapons in the city, birthplace of the Muslim Prophet Muhammad, leading to fears a strike was planned in Mecca.

The United States joined countries around the world in expressing condolences and pledging to stand by Saudi Arabia in the war on terror. Deputy Secretary of State Richard Armitage (search), who was in Egypt on Monday after visiting Saudi Arabia the previous day, said the attack was more evidence the war on terror was far from over.

"Our president, after the events of Sept. 11, said he was preparing our nation for a long war, and the more we looked at the phenomenon of Al Qaeda, the more we became convinced there is going to be a long struggle," Armitage said.

In Riyadh, Armitage pledged Americans "will be fully participating partners, if that is the desire of the kingdom of Saudi Arabia" in its anti-terror fight.

Armitage, echoing initial Saudi assessments, said he was "personally quite sure" Al Qaeda was behind the car bombing.

Such attacks appear to be directed "against the government of Saudi Arabia and the people of Saudi Arabia," Armitage said, adding that he expected more.

The Saudi ambassador to Britain, Prince Turki al-Faisal, cited similarities between Saturday's bombings and previous Al Qaeda strikes. Saudi officials blame Al Qaeda for a series of car bombings May 12 on three Riyadh compounds housing foreigners. Those attacks killed 35 people, including nine homicide bombers.

Fox News' Teri Schultz and The Associated Press contributed to this report.