US President, Donald Trump has called on Russia to stop “destabilising” Ukraine and other countries and end support for “hostile regimes” such as those in Syria and Iran.
Speaking in the Polish capital Warsaw, Mr Trump urged Russia to “join the community of responsible nations”.
The Kremlin rejected his comments.
The US leader has travelled to Hamburg for the G20 summit, where he will meet Russian President Vladimir Putin for the first time.
He also faces differences with other leaders, including German Chancellor, Angela Merkel, who said last week that the G20 would focus on the Paris climate deal, which the US has withdrawn from.
In Warsaw, Mr Trump argued that the future of Western civilisation itself was at stake and asked whether the West had the “will to survive”.
Up to 100,000 protesters are expected over the two-day event and police have warned of potentially violent clashes. They have already confiscated a number of homemade weapons.
“It’s important because you have the biggest meeting of all of the leading rulers of the main countries in the world – the G20 – and I don’t like some of the politics that they’re doing, especially that of [Recep Tayyip] Erdogan, of Putin and of Trump,” one protester said.