Special Counsel Robert Mueller warned he could issue a subpoena for Donald Trump to appear before a grand jury as part of a probe into alleged Russian election meddling, US media report.

Mr Mueller suggested the move during talks with Mr Trump’s lawyers in March.

He said the subpoena would compel the president to face investigators, the Washington Post reports.

It is believed to be the first time the special counsel raised the possibility of forcing Mr Trump to testify.

What was said during the talks?

During the meeting in March, Mr Trump’s lawyers insisted that the president was under no obligation to face questions by federal investigators in relation to the Russia inquiry, according to the Washington Post, which cited four people familiar with the encounter.

However Mr Mueller’s team reportedly responded by suggesting they would issue a subpoena if Mr Trump declined. They agreed to provide the president’s lawyers with more specific information about the questions they wished to ask Mr Trump.

Trump-Russia saga in 200 words

Key questions in the affair answered

The president’s former lawyer, John Dowd, also told Reuters news agency on Tuesday that Mr Mueller mentioned at the meeting the possibility of forcing Mr Trump to face questions.

Mr Dowd, who resigned about a week and a half after the meeting, said he told investigators that the probe was not “some game”, adding: “You are screwing with the work of the president of the United States.”

What was leaked?

On Monday, the president criticised the New York Times for publishing more than 40 questions that Mr Mueller wanted to ask him as part of the Russia investigation.

He tweeted on Tuesday that the leaking of the inquiry questions to the media was “disgraceful”, adding: “It would seem very hard to obstruct justice for a crime that never happened.”

Mr Mueller’s current list reportedly ranges from questioning the president’s motivations in dismissing former FBI director James Comey last May to his treatment of Attorney General Jeff Sessions after his recusal from the Russia investigation.

What we learn from Mueller’s questions

Who’s who in Russia-Trump inquiry?

One of the questions directly refers to Paul Manafort, the former Trump campaign chairman, asking what knowledge Mr Trump may have had about Mr Manafort’s outreach to Russia.

Mr Mueller also plans to ask Mr Trump about his election campaign’s possible co-ordination with Russia, according to the New York Times, which said it obtained the list from someone other than the president’s lawyers.

White House spokesman Raj Shah said the Times report was “troubling”.

“The entire premise of this investigation was on this topic of collusion and the overwhelming focus of the questions is not on that topic,” he said.

What is Robert Mueller investigating?

The special counsel is looking into Russia’s efforts to interfere in the 2016 US election, whether there was any collusion between the Kremlin and Mr Trump’s election campaign and whether the president unlawfully tried to obstruct the inquiry.

Mr Mueller was appointed special counsel following Mr Trump’s firing of FBI director James Comey last May.

What does the special counsel do?

The president insists there was no collusion between his election campaign and the Russians.

US media reported that sources familiar with the case said Mr Mueller informed Mr Trump’s attorneys in March that he is a subject of the investigations, but not a criminal target.

It remains unclear when Mr Mueller will request a meeting with the president.