In this image taken from video U.S. President Donald Trump, centre left, meets with the Russian President Vladimir Putin, centre right, during the G20 summit in Hamburg, Germany. Picture: Steffen Kugler/German Government via AP

Hamburg - US President Donald Trump and Russian President Vladimir Putin's first encounter at a leaders' retreat in Hamburg, Germany was caught on tape.

The two leaders were seen shaking hands and exchanging pleasantries ahead of their planned formal, sit-down meeting in video posted to Facebook by the German Cabinet.

As officials gathered around a table, Trump outstretched his hand to Putin and then patted his elbow. Both men smiled.

Another brief video clip shows Trump casually patting Putin on the back as they stand side by side.

"They shook each other's hand and said that they would soon hold a separate meeting, would soon see each other," Kremlin spokesman Dmitry Peskov told a conference call with reporters.

Putin and Trump are due to hold detailed one-on-one talks on the sidelines of the summit later on Friday.

When asked if Putin was looking forward to the talks and whether he had lots of questions for Trump, Peskov said he did.

The Russian leader had been fully briefed about Trump's description on Thursday of Moscow's behaviour as destabilising, Peskov added, and would take that and other remarks by US officials into account. 

Reuters and AP