Former House Speaker Nancy Pelosi has been taken to hospital after she "sustained an injury" during an official engagement in Luxembourg.
Ms Pelosi, 84, was in Europe to mark the 80th anniversary of the Battle of the Bulge in the Second World War.
Her spokesman, Ian Krager, said in a statement that she is "currently receiving excellent treatment from doctors and medical professionals" and is unable to attend the remainder of events on her trip.
He did not describe the nature of her injury or give any additional details.
Ms Pelosi "looks forward to returning home to the US soon," Mr Krager said.
Ms Pelosi, who was first elected in 1987 and served as speaker twice, stepped down from her leadership post two years ago but remained in Congress and was re-elected to represent her San Francisco district in November.
She has remained active in the two years since she left the top job, working with Democrats behind the scenes and in public and attending official events.
The former speaker's unspecified injury comes days after Senate Republican Leader Mitch McConnell tripped and fell in the Senate, spraining his wrist and cutting his face.
Mr McConnell, who is stepping down from his leadership post at the end of the year, missed Senate votes on Thursday after experiencing some stiffness in his leg from the fall, his office said.