"Maduro will only use this military support to further repress the people of Venezuela; perpetuate the economic crisis that has destroyed Venezuela's economy; and endanger regional stability," US national security advisor John Bolton said of the Russian presence.

"We call on the Venezuelan military to uphold its constitutional duty to protect the citizens of Venezuela," he said in a statement.

The statement did not specify what exact actions the US wanted the Venezuelan military to take, but Trump has said its army chiefs could play a "vital role" in the country's future if they abandoned their support for Maduro

The statement Friday warned that any effort by "actors external to the Western Hemisphere" to deploy military assets to Venezuela with an eye to military operations would be considered "a direct threat to international peace and security in the region."

The United States and 50 other countries say that Maduro, a leftist firebrand presiding over a crumbling economy, is no longer the legitimate leader and have recognized opposition leader Juan Guaido as interim president.

But Maduro, backed by Russia and China, has held on to power and on Thursday his regime announced a ban on Guaido holding public office.

US President Donald Trump earlier called on Russia to "get out" of Venezuela.

Russia has said that its forces, described as military experts providing technical help, will stay "for as long as needed," calling the US effort in Venezuela an attempted coup.

Two Russian military planes landed at the main airport outside Caracas on Saturday and offloaded an estimated 100 troops and several tons of equipment.