The U.S. and Canada closed their embassies in Kyiv, amid the threat of a Russian attack on Ukraine's capital, but the State Department announced that it would reopen the embassy on Thursday.
The State Department said it expects its embassy in Kyiv to return to normal operations on Thursday.
Spokesman Matthew Miller declined to say what kind of threat had forced the embassy to shut down on Wednesday as a safety precaution.
"We take the safety and security of our personnel... extremely seriously," Miller said.
The US mission had closed a day after Moscow vowed to respond to Ukraine's firing of long-range US-supplied missiles at Russian territory for the first time in the nearly three-year war.
"The US Embassy in Kyiv has received specific information of a potential significant air attack on November 20," the embassy had said on its website.
The embassy was closed on Wednesday and embassy employees were instructed to shelter in place, a day after Ukraine used American missiles to hit a target inside Russia in what Moscow described as an escalation in the war.
Canada also temporarily closed its embassy in Kyiv following a U.S. advisory about a "potential significant air attack" on Ukraine, according to a media report Wednesday.
The advisory, which urged citizens to shelter during air alerts, was followed by similar closures of the Spanish, Italian and Greek embassies in Ukraine, according to CTV News.
The warning came one day after Ukraine, for the first time, attacked the Russian territory with US-made ATACMS missiles.
CTV News said Ukraine's military intelligence agency dismissed the warning as Russian misinformation and "this message is a fake."
It advised citizens, however, to remain cautious and heed air raid sirens.
Ukraine on Tuesday used U.S. ATACMS missiles to attack an arms depot inside Russia, making use of newly granted permission from the outgoing administration of U.S. President Joe Biden on the 1,000th day of Russia's full-scale invasion of Ukraine.
Russia has been signaling to the United States and its allies for weeks that if they give permission to Ukraine to strike deep into Russian territory with Western-supplied missiles then Moscow will consider it a major escalation.
"Out of an abundance of caution, the embassy will be closed, and embassy employees are being instructed to shelter in place," the U.S. Department of State Consular Affairs said in a statement on the embassy's website.
"The U.S. Embassy recommends U.S. citizens be prepared to immediately shelter in the event an air alert is announced."
The Kremlin said it had no comment.
Russian foreign intelligence chief Sergei Naryshkin said in an interview published on Wednesday that Moscow would retaliate against NATO countries that facilitate long-range Ukrainian missile strikes against Russian territory.
