Willing to testify before Senate on Trump's impeachment trial, says Bolton

Months after he was fired by US President Donald Trump, former national security advisor John Bolton on Monday said he is ready to testify before the Senate on Trump's impeachment trial.

The surprising move by 71-year-old Bolton adds a new dimension to the ongoing impeachment proceedings against Trump, who is only the third president in the US' history to face such an attempt to remove an elected president from power.

"I have concluded that, if the Senate issues a subpoena for my testimony, I am prepared to testify," he said in a statement on Monday night.

The House, he said, has concluded its Constitutional responsibility by adopting articles of Impeachment related to the Ukraine matter.

"It now falls to the Senate to fulfil its Constitutional obligation to try impeachments, and it does not appear possible that a final judicial resolution of the still-unanswered Constitutional questions can be obtained before the Senate acts," he said.

Bolton said accordingly, "since my testimony is once again at issue, I have had to resolve the serious competing issues as best I could, based on careful consideration and study."