The embassy shut down because of an imminent al-Qaida attack. In an announcement on its Web site, the embassy said Yemeni actions "have addressed a specific area of concern, and have contributed to the Embassys decision to resume operations."
The reopening comes a day after Yemeni security forces clashed with al-Qaida fighters, killing two, in the latest sign the embattled, longtime president is making good on vows that his country will cooperate with the United States in fighting the terror network.
The Yemeni Interior Ministry said Tuesday it had increased security measures around embassies.
"There is nothing to fear from any threats of terror attack," the ministry said in a statement. "Security is good in the capital and the provinces, and there is no fear for the lives of any foreigner or foreign embassy."
Washington is embracing Yemeni President Ali Abdullah Saleh in the battle against al-Qaida's offshoot here. With an injection of U.S. counterterror aid and help for its security forces, Yemen's government has vowed in recent weeks to work with the U.S. in stamping out the estimated hundreds of al-Qaida fighters who have built up strongholds in the country's remote regions. Last month, with U.S. help, it carried out its heaviest strikes in years against al-Qaida hideouts, claiming to have killed 30 militants.
The renewed determination brought praise Monday from U.S. Secretary of State Hillary Rodham Clinton. "The United States commends Yemen for the recent actions it has taken to disrupt (al-Qaida) networks and we are reiterating our commitment to assist in those efforts," she said.
In Monday's clashes, Yemeni security forces attacked a group of al-Qaida militants moving through the mountainous area of Arhab, northeast of the capital, security officials said.
Among them was Nazeeh al-Hanaq, a senior figure on Yemen's most wanted list. He escaped, but two fighters with him were killed, the officials said, speaking on condition of anonymity because they were not authorized to talk to the press.
In addition, Yemeni forces arrested five others in the capital and the western region of Hodeida, the interior ministry said.
Monday's battle came as the U.S. and British embassies in San'a were shut down for a second day after threats of an imminent al-Qaida attack. Other Western embassies took similar steps Monday: The French and Czech embassies were closed to the public, while the Spanish and German embassies limited the number of visitors, their governments said.
The British Foreign Office said its embassy was "operational" Tuesday - meaning staff had returned to work - but it remained closed to the public. Germany, France and Spain said their embassies' status remained unchanged.
While the U.S embassy reopened Tuesday, it said the threat of terrorist attacks against American interests remained high and urged its citizens in Yemen to be "vigilant and take prudent security measures."
The fight against al-Qaida in Yemen has taken on greater urgency since the failed Christmas attempt to bomb an American passenger jet. Umar Farouk Abdulmutallab, the 23-year-old Nigerian man who tried to destroy a Detroit-bound airliner, told U.S. investigators he received training and instructions from al-Qaida operatives in Yemen.
For the U.S., the situation in Yemen raises parallels with Iraq and Afghanistan, where Washington has had to go beyond military action to infuse economic help while pushing political reform on sometimes reluctant political leaders in hopes of undermining support for militants.
Observers warn that Saleh's 31-year rule is buckling under the weight of multiple crises, deep poverty and widespread corruption. The government has full control only around the capital, leaving much of the mountainous nation to heavily armed tribes, some of which have given refuge to al-Qaida fighters.
"Saleh is facing the most difficult time of his presidency," said Ali Seif Hassan, director of a Yemeni organization that mediates government-opposition dialogue.
"Now he faces the decision whether to keep going as he has, all the way to becoming a failed state, or to make the hard choices to avoid that," he said.
Over the weekend, President Barack Obama vowed that his administration has "made it a priority to strengthen our partnership with the Yemeni government - training and equipping their security forces, sharing intelligence and working with them to strike al-Qaida terrorists."
The United States hiked its counterterrorism aid to Saleh's government, from none in 2008 to $67 million last year - an amount Washington says will double in 2010.
But Saleh's government says the United States and other nations must also provide economic aid to tackle deepening poverty that it says fuels support for al-Qaida among Yemen's swelling population of 22 million.
The mercurial Saleh has held onto power for 31 years in this fragmented nation by relying on a system of manipulation - centralizing power within his family while buying off rivals and unruly tribesmen, Yemeni and American observers say.
At times, that has meant forging alliances with Islamic extremists, and Saleh has frustrated U.S. officials in recent years by freeing jailed al-Qaida figures on promises they would not engage in terrorism. Several top militants have since broken those promises.
