Thousands of marchers protested in Venezuela on Wednesday to try to force socialist President Nicolas Maduro from power as tension grew between Russia and the United States over the political standoff in the OPEC-member nation.

Opposition leader Juan Guaido had called for the "largest march" in Venezuela's history and on Tuesday asked the military for their backing, but the armed forces leadership has so far remained loyal to Maduro, who has been in power since 2013.

"If the regime thought we had reached maximum pressure, they cannot even imagine," Guaido told thousands of cheering supporters in eastern Caracas. "We have to remain in the streets."