Secretary of State Mike Pompeo on Tuesday promised the world a "smooth transition" after US elections but refused to recognize President-elect Joe Biden's victory, saying Donald Trump will remain in power.

"There will be a smooth transition to a second Trump administration," Pompeo said in an at times testy news conference when asked about contacts with the Biden team.

"The world should have every confidence that the transition necessary to make sure that the State Department is functional today... with the president who is in office on January 20 a minute after noon will be successful," he said, referring to the date of the presidential inauguration.

World leaders including almost all US allies have congratulated Biden, who has achieved unassailable leads in key states as well as a commanding edge in the nationwide popular vote.

US Secretary of State Mike Pompeo, seen here in November 2019, has defended "restraint" on Venezuela
US Secretary of State Mike Pompeo, seen here in November 2019, has defended "restraint" on Venezuela AFP / Kenzo TRIBOUILLARD

But Trump has refused to concede the November 3 election and has alleged massive fraud, calling for recounts and legal action.

Asked if the United States can still issue statements calling for free elections around the world, Pompeo said the question was "ridiculous."

"This department cares deeply to make sure that elections around the world are safe and secure and free and fair, and my officers risk their lives to ensure that that happens," he said.