The American ambassador to Belarus has left the embassy in the capital, Minsk, because of a diplomatic dispute.
Ms Stewart met opposition activists before she left
A spokesman at the embassy told the BBC that Karen Stewart had not been expelled and her absence was temporary.
Belarus announced last Friday it was withdrawing its ambassador to Washington and asked the US to follow suit. The US initially refused.
Minsk has accused the US of violating agreements aimed at normalising diplomatic relations.
The Belarussian authorities accuse the US of tightening sanctions on the country's state-controlled oil-processing and chemicals company, Belneftekhim.
Our correspondent in the region, Gabriel Gatehouse, said that for four days the two countries were "in a kind of diplomatic limbo".
As well as sanctions on individual companies, both the US and the EU have imposed travel bans on Belarussian President Alexander Lukashenko and some of his top officials.
They have demanded that President Lukashenko frees political prisoners, and allows more democratic freedom, before normal relations can be restored.
Our correspondent says in recent months there have been signs of a thaw, with the release of some opposition activists.
But there has been no response to pressure from Washington to release Alexander Kozulin, who challenged Mr Lukashenko in the 2006 presidential election, and was arrested during a post-election protest.
Mr Kozulin was allowed to attend his wife's funeral, but he was then returned to prison.
Before Karen Stewart left, she met opposition activists and human rights campaigners.
In a statement, the embassy said the United States held out the possibility of a thaw in relations: "Following the unconditional release of all political prisoners, the United States stands ready to explore steps to improve our bilateral relations."