The US has been accused of sending troops to fight Russian forces in Syria and Ukraine.
However, the US government has argued that it is just defending its own interests.
The US says its role is to assist the US and its allies in a global conflict and that it does not support the use of force by anyone other than those who have signed up to it.
Here are the key points: Russia has been arming, training and funding groups fighting against the US in Syria, including groups who are fighting the US, Turkey and the Gulf states.
The Russian military has also been involved in the battle in Yemen and has been fighting the Saudi-led coalition there, as well as supporting groups fighting the Syrian government.
Russia also denies supporting the rebel groups in eastern Ukraine.
Russia has deployed military personnel to Syria, the largest of which has been a contingent of military advisors, and has sent weapons and military advisers to Turkey, a NATO member.
Russia’s military intervention in Syria has been accompanied by air strikes and the deployment of troops on its borders with Ukraine.
It has also provided military advisers and logistical support to Kurdish forces fighting the Russian-backed Syrian government in Iraq.
Russia says it does have a plan to defeat the US-led alliance.
But US officials say it has been far from a success.
US President Donald Trump and Russian President Vladimir Putin have been embroiled in a number of contentious encounters in recent months.
US officials have said they are worried about the impact of the Russia intervention on US-Russian relations, which are already at an all-time low, and are concerned that Moscow could try to use the conflict to advance its interests elsewhere in the world.
US Secretary of State Rex Tillerson said in July that Russia has the ability to “destroy NATO”.
“We do have a strategy for dealing with this,” Tillerson said.
“But we can’t make the Russian strategic decision to invade another country just to make sure it doesn’t get attacked by a coalition of other countries.”
US and European officials have also said that the conflict has been destabilising the Middle East, particularly in the north of the country.
But the Syrian conflict has also destabilised the Balkans.