Donald Trump will meet Vladimir Putin in Vietnam tomorrow, the Kremlin has said.

The leaders, who discussed allegations of Russian meddling in the US election during their first face-to-face meeting in July, are both planning to attend the Asia-Pacific Economic Cooperation summit in the city of Danang.

Their paths will cross this week amid an intensifying investigation into claims of collusion between the Republican's election campaign and Moscow.

Mr Trump said before embarking on his Asia tour that he may meet with Mr Putin in Vietnam about Syria, Ukraine and North Korea.

Moscow is thought to be keen on talks as it bids to improve strained US-Russia relations.

Kremlin aide Yuri Ushakov told Russian news agencies on Thursday that a meeting would happen on Friday but said the timing and format had yet to be finalised.

"Right now the time of the meeting is being agreed. It will be on the 10th [of November]," Mr Ushakov told agencies.

Kremlin spokesman Dmitry Peskov said plans for formal talks remained under discussion but added the leaders' paths would cross at some point.

He added: "As for the content of the meeting, there is no agreed agenda."

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But US Secretary of State Rex Tillerson, on a visit to Beijing with the President, questioned whether the two leaders would have enough to discuss to warrant formal talks.

"There's never been an agreement, certainly not to a full bilat[eral]," he said, although he added it would not be unusual if the two men had a spontaneous "pull-aside meeting" if they bumped into each other.

"The question is whether we've got sufficient substance [for a more formal meeting] and we're working with the Russians, as you know, on a number of difficult areas," said Mr Tillerson.

"We're in contact with them and the view is that the two leaders are going to meet if there's something sufficiently substantive to talk about that would warrant a formal meeting."

Mr Putin and Mr Trump spoke in person for more than two hours during their first meeting at the G20 summit in Hamburg in July.

The Russian President assured Mr Trump Moscow had not meddled in the 2016 election, although the White House denied reports the US leader had accepted his word.

They also discussed Syria, Ukraine, terrorism and cyber-security.

But ties have soured since then.

In August Mr Trump grudgingly signed off on new sanctions against Russia, a move Moscow said ended hopes for better relations. Mr Putin subsequently ordered Washington to cut its embassy and consular staff in Russia by more than half.

Any meeting between the two heads of state this week would come under close scrutiny as special counsel Robert Mueller's probe into Russian election meddling deepens by the day.

Last week three former members of Mr Trump's team - including ex-campaign manager Paul Manafort - were charged by Mr Mueller.