US Senator and former First Lady Hillary Rodham Clinton has collapsed during a public appearance in Buffalo, New York state.
The New York senator complained of feeling unwell
She fainted during an address to a chamber of commerce lunch.
An aide to Sen Clinton, 57, said she had a virus and felt unwell, but she recovered to give another speech, as planned, later on.
The senator was not taken to hospital despite earlier reports she had been hospitalised, our correspondent says.
"Senator Clinton is suffering from a stomach virus," a statement on her Senate website said.
"She wasn't feeling well while speaking at an event in Buffalo, New York, this morning. She felt weak, needed to sit down, and then fainted briefly.
HILLARY RODHAM CLINTON
Born 26 October, 1947 in Chicago
Attended Wellesley College
Graduated from Yale Law School in 1973
Married Bill Clinton in 1975
Campaigner for expanding health insurance coverage and woman's rights
Elected New York senator in 2000
Mrs Clinton told the crowd she was feeling weak and had had a stomach virus, Colleen DiPirro, president of the Amherst Chamber of Commerce, told a local radio station.
She started to speak then collapsed, Ms DiPirro said.
The senator received medical attention at the scene and was able to fulfil another speaking engagement at a Catholic college later on.
"It wasn't as dramatic as it sounds," the Associated Press news agency quoted Mrs Clinton as saying after the 30-minute speech.
The senator has been widely tipped as a leading candidate for the Democratic presidential nomination in 2008.
Last September her husband, former US President Bill Clinton, underwent quadruple bypass heart surgery.