John Bolton has been called in to testify in the impeachment inquiry into US President Donald Trump.
The former National Security Adviser has been summoned by the House of Representatives investigators.
The US President is being investigated for pressuring Ukraine to investigate former US Vice-President Joe Biden and his son.
Trump denies the claims.
Bolton, who has spoken against the president on the matter, has been asked to testify on November 7.

Mediator Pakistan says US, Iran expected to sign initial deal within 24 hours
India Air Force plane crash kills all five onboard
Ukrainian strike kills one, wounds 3 in southern Russia
Trump says US military strike killed leader of Venezuela's Tren de Aragua gang
Qatar rejects media report on energy production decisions
Trump says Iran war deal close as Strait of Hormuz tensions linger
Victims' families mark Air India crash anniversary with prayers and tributes
Ebola outbreak spreads to crowded displacement camp in Congo
