U.S. Secretary of State Mike Pompeo on Sunday lashed out at Venezuelan President Nicolas Maduro, saying his administration's "days are numbered."

"We’re very hopeful in the days and weeks and months ahead the Maduro regime will understand that the Venezuelan people have made its days numbered," Pompeo told in an interview with Fox News on Sunday.

His remarks came a day after at least four people were killed and 200 others injured during anti-government protests in Venezuela. Fifty-one people were also arrested as they clashed with security forces at the Colombian border.

Protesters were calling for the government to open borders and allow the U.S. humanitarian aid into the South American country.

In his remarks, the secretary called Maduro "the worst of the worst of a tyrant".

"I think the Venezuelan people are seeing that. We saw yesterday the military begin to see it as well," he added.

Asked if a military force will be used against Maduro, Pompeo said every option is on the table.

"We are going to do the things that need to be done to make sure that the Venezuelan people’s voice, that democracy reigns and that there is a brighter future for the people of Venezuela," Pompeo added.

Venezuela has been rocked by protests since Jan. 10, when President Nicolas Maduro was sworn in for a second term following a vote boycotted by the opposition.

Tensions escalated when Juan Guaido, who heads Venezuela’s National Assembly, declared himself acting president Jan. 23, a move which was supported by the U.S. and many European and Latin American countries.

Turkey, Russia, Iran, Cuba, China, and Bolivia reiterate support for Venezuelan President Maduro, who vowed to cut all diplomatic and political ties with the U.S. following the diplomatic spat.