The White House on Tuesday condemned the presence of foreign military forces in Libya and said there is no "winning side" in the its complex civil war.

"The United States is deeply troubled by the escalating conflict in Libya. We strongly oppose foreign military involvement, including the use of mercenaries and private military contractors, by all sides," President Donald Trump's national security advisor Robert O'Brien said in a statement.

O'Brien, who returned to work Tuesday after recovering from the coronavirus, said the international power struggle in energy rich, strategically placed Libya posed "grave threats to regional stability and global commerce."

He said that Trump had spoken with several other countries' leaders about Libya recently and that "it is clear there is no 'winning' side."

"Libyans can win only if they come together to reclaim their sovereignty and rebuild a unified country," Trump's advisor said.

Last month, the Pentagon released what it said was satellite photograph evidence of Russian military hardware deployed in the city of Sirte.

The city is held by rebel commander Khalifa Haftar, who is supported by Egypt, Russia and the United Arab Emirates.

The UN-recognized Government of National Accord (GNA), which is seeking to wrest back full control from Haftar, is backed by Turkey.

Libya has been mired in chaos since the 2011 overthrow of longtime dictator Moamer Kadhafi, with rival political and armed groups battling for control.