Image copyright
EPA
It is unclear if John Bolton will appear before the inquiry
Former US National Security Adviser John Bolton has been summoned to testify in the impeachment inquiry into President Donald Trump.
House of Representatives investigators have invited him to appear next month.
Mr Trump has denied using the power of his office to pressure Ukraine to investigate former US Vice-President Joe Biden and his son.
Mr Bolton likened the alleged proposal to a “drug deal”, according to witness testimony.
It is unclear if Mr Bolton, who left his position in September after falling out of favour with the president, will appear as scheduled on 7 November.
Mr Bolton was also alarmed about the interactions of President Trump’s private lawyer Rudy Giuliani with Ukraine, according to US media.
A Department of State diplomat reportedly told House impeachment investigators that Mr Bolton had warned him about Mr Giuliani’s influence with the president on Ukraine.
Mr Giuliani acknowledged last month in a TV interview having asked Ukraine to investigate Mr Biden.
The former US vice-president is a leading Democratic candidate to challenge Mr Trump for the White House next year.
Media playback is unsupported on your device
Mr Bolton’s anger over efforts to pressure Ukraine for political help had reportedly led to heated confrontations inside the White House last summer.
Some of those details have also emerged in other witness testimonies, including that of President Trump’s former top aide to Russia, Fiona Hill.
Ms Hill, according to US media reports, testified that Mr Bolton was so alarmed that he asked her to alert White House lawyers about an alleged rogue effort by Gordon Sondland, the US ambassador to the EU, Mr Giuliani and Mick Mulvaney, the acting White House chief of staff.
“I am not part of whatever drug deal Sondland and Mulvaney are cooking up,” Mr Bolton reportedly told Ms Hill.