US Secretary of State Hillary Clinton is in hospital being treated for a blood clot, linked to concussion from a fall earlier this month.
The 65-year-old has been out of the spotlight since mid-December after she fainted and banged her head while recovering from a stomach virus.
Mrs Clinton is being given anti-coagulants in a hospital in New York.
Officials say her condition is improving and have played down suggestions that it is anything more serious.
The clot was discovered by doctors monitoring her health following the fall. She is expected to be in hospital for the next 48 hours.
She had been due back at her desk next Monday.