US President-elect Donald Trump has tapped his aide Richard Grenell to be presidential envoy for special missions.

In a social media post on Saturday, Trump said Grenell "will work in some of the hottest spots" around the world, including Venezuela and North Korea.

Grenell served as spokesperson at the US mission to the United Nations under the George W. Bush administration. He also served as the US ambassador to Germany and acting director of national intelligence during Trump's first term.

Grenell is regarded as a foreign policy hawk. As ambassador, he suggested the US should reduce the number of its troops stationed in Germany.

Grenell is known as a close aide to the president-elect. He accompanied Trump to his talks with Ukraine's President Volodymyr Zelenskyy in September. He also worked to reach out to Arab American voters during the presidential election.

US media had suggested Grenell might be picked for such positions as national security adviser or special envoy for Ukraine in the second Trump administration.