President Trump and Russia's President Vladimir Putin talk during the family photo session at the APEC Summit in Danang, Vietnam.

Vienna is one of the cities being considered as the venue for a possible summit between Russian President Vladimir Putin and his U.S. counterpart Donald Trump, Kremlin spokesman Dmitry Peskov told reporters on Saturday.

Putin said last month that the proposed summit between him and Trump was not working out for now and was beset by problems.

Trump said in March that the two leaders would meet soon, but since then already poor ties between Washington and Moscow have deteriorated further over the conflict in Syria and the poisoning of a former Russian spy in Britain.