Vladimir Putin said Donald Trump's drive to win another presidential term might complicate the situation

Russian President Vladimir Putin said on Thursday he was ready to hold talks with Donald Trump if that was what his U.S. counterpart wanted, but added that Trump's re-election campaign could complicate U.S.-Russia relations.

Trump has said he expects to meet Putin at a G20 summit in Osaka, Japan, next week, though Moscow has so far said it has yet to receive a formal invitation for such talks.

U.S.-Russia ties remain strained by everything from Syria to Ukraine and Venezuela, as well as by allegations of Russian interference in U.S. politics, which Moscow denies.

Putin said this month that relations between Moscow and Washington were getting worse and worse.

"Dialogue is always good, there's always demand for it," said Putin during his annual question-and-answer session when quizzed about talks with Trump.

"Sure, if the American side shows interest ... we are ready for dialogue."

The Russian leader said the two countries had a lot to talk about, including strategic nuclear stability. A landmark arms control treaty is coming up for renewal, while both sides have said they are quitting the 1987 Intermediate-range Nuclear Forces (INF) Treaty, stoking fears of a wider arms race.

Putin said Trump's drive to win another presidential term might complicate the situation, however.

"We all understand and see what is going on in domestic politics in the United States," said Putin. "Even if the president wants to take steps towards us, wants to talk about anything, there are a huge number of limitations.

"Even more so now as the current head of state will make all his statements with his election campaign in mind. He has already started the campaign, so everything will not be simple in our relations," Putin said.

The Russian leader said talks, if they took place, could help re-establish what he called normal relations between Russia and the United States, including on the economy. He also said he wanted the two countries to talks about cyber security.