Donald Trump and Vladimir Putin briefly shook hands at a gala dinner during an Asia-Pacific summit yesterday after days of frenzied speculation on whether the two would meet.

It is still unclear whether the pair plan to hold substantive talks during their visit to Vietnam following days of mixed messages from the Kremlin and the White House.

Relations between Moscow and Washington have plummeted as a US probe has accused Trump's former campaign aides of secretly meeting Kremlin-connected officials - a charge Russia denies.

Trump had previously indicated that he hoped to hold talks with his Russian counterpart during his Vietnam visit, to pressure Moscow into supporting his moves to challenge North Korea's nuclear ambitions.

Both leaders are attending the Asia Pacific Economic Cooperation (APEC) forum in the Vietnamese city of Danang.