Both Washington and Moscow have troops on the ground in Syria backing opposing sides of the war that has ravaged the Middle Eastern country since 2011.

Russia's war in Ukraine since February has exacerbated geopolitical tensions with the United States.

But on Saturday morning, US and Russian patrol routes intersected at an oil field near the town of Qahtaniyah in the northeastern province of Hassakeh, according to AFP correspondents.

It was not the first time they cross paths in the Kurdish-held region but, instead of just zipping past each other, the convoys stopped and soldiers stood side by side as they spoke and posed for pictures.

Several troops even exchanged small patches worn on their uniforms as momentos of the interaction, the correspondents said.

It was a "very rare moment", said Syria expert Samuel Ramani, and a sign "that Russia and the US still want deconfliction in Syria".

A staunch opponent of the Syrian regime, Washington first deployed troops in northeast Syria in 2014 as part of a coalition to combat the Islamic State group.

The Russian military, for its part, has backed the government of President Bashar al-Assad since 2015, but did not deploy forces in the northeast until 2019, following a Turkish invasion against Kurdish fighters.

Deconfliction channels have been in place since 2015 to prevent any clash between the Russians and the Americans.

The presence of Russian troops has also helped US forces avoid a face-off with Syrian regime forces.