Donald Trump said he did not instruct General Mike Flynn, his former national security adviser, to talk to Russia about the possibility of easing US sanctions on Moscow – but he would have done so if he had not thought it was already being done.

General Flynn resigned earlier this week after it emerged that, before taking his post, he had spoken to Sergey Kislyak, Moscow’s ambassador to the US, about the issue of sanctions.

It is illegal for a private citizen to conduct diplomacy on behalf of the US.

The retired general had previously denied sanctions were discussed during the conversation - a claim he repeated during private talks with Vice President Mike Pence.

Mr Pence then relayed that information to members of the media.

Asked about the issue during a White House press conference, Mr Trump defended General Flynn and said his only mistake had been lying to Mr Pence about the nature of the conversations.

Responding to a question on whether he would have sacked him if the details of his conversation with the Russian ambassador had not leaked, Mr Trump said: “No, I fired him because of what he said to Mike Pence. Very simple.”

The Republican was also asked whether he had instructed Mr Flynn to raise the issue of sanctions with Russia.

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He replied: “No I didn’t…Mike was doing his job. He was calling countries and his counterparts.

“So it certainly would have been OK with me if he did it. I would have directed him to do it if I thought he wasn’t doing it.