Russian President Putin meets with former U.S. Secretary of State Kissinger in Moscow Thomson Reuters By Maria Tsvetkova

MOSCOW (Reuters) - Donald Trump and Vladimir Putin have an opportunity to mend their countries' ties when they meet next week, former top U.S. diplomat Henry Kissinger said on Friday, a day after he followed up a meeting with the U.S. president by having talks with Putin.

Expectations that Trump's election would bring a thaw in icy relations between Moscow and Washington have been put on hold, with the White House embroiled in a domestic row over Trump associates' Russia ties.

The U.S. and Russian leaders are to have their first face-to-face encounter next week at a G20 summit in Hamburg.

At a previous moment of heightened tension between Moscow and Washington, in the 1960s, Kissinger acted as a back-channel intermediary, passing messages to the leadership of the Soviet Union on behalf of U.S. President Richard Nixon.

The Kremlin on Friday denied that Kissinger, who is visiting Moscow and met Putin behind closed doors on Thursday, was acting as a go-between this time.

Speaking at an international affairs conference in Moscow, Kissinger said of the planned Trump-Putin meeting: "I believe that at this moment our two countries have a responsibility, and an opportunity, to make significant progress not just by improving relations, but by improving situations around the world through cooperative efforts."

"Tensions between Russia and the United States ... have happened often before and they have been overcome often before," Kissinger, 94, said. He did not take questions from reporters at the event.

Asked if Kissinger was providing a back-channel between the Kremlin and the White House, Kremlin spokesman Dmitry Peskov said: "He didn't try. That did not happen."

He said the Kissinger-Putin meeting was strictly private and declined to disclose what the two men talked about.

In May, Trump granted a White House audience to Kissinger. The U.S. leader said he and Kissinger would talk about Russia, among other issues.

Speaking at the same Moscow event as Kissinger on Friday, Russian Foreign Minister Sergei Lavrov said that the significance of the planned Putin-Trump Hamburg meeting was that "the abnormal period in our relations when the leaders only speak by telephone will be overcome."

"Judging by their telephone conversations, they have a desire to get beyond this abnormality and start seeking agreement on specific issues."

(Writing by Christian Lowe; Editing by Andrew Osborn)