The United States said Thursday that it backed democratic principles in Pakistan after former prime minister Imran Khan, an outspoken critic of Washington, was slapped with charges.

"We support the peaceful upholding of democratic, constitutional and legal principles," State Department spokesman Vedant Patel told reporters.

"The United States values our longstanding cooperation with Pakistan and has always viewed a prosperous and democratic Pakistan as critical to US interests," he said.

He declined to weigh in more specifically on charges against Imran Khan, who was ousted in a parliamentary vote in April but hopes to stage a comeback in elections.

Imran Khan has staged rallies to rail against his successor, Shehbaz Sharif, and has alleged a conspiracy against him orchestrated by the United States, allegations repeatedly dismissed in Washington as baseless.

Imran Khan was granted interim bail after being slapped with charges by an anti-terror court over comments against a magistrate over the detention of an official in the former prime minister's party.

A couple of days ago, the United States had also declined to comment on the terrorism-related charges against Imran Khan, saying it does not side with a political party and it is an internal matter of Pakistan.

US State Department spokesperson Ned Price had said that the country was “of course” aware of the reports about the charges. But he said this is a matter of the Pakistani legal and judicial system.

“It is not directly a matter for the United States, and that’s because we don’t have a position on one political candidate or party versus any other political candidate or party.”

The State Department spokesperson added that the US supports the “peaceful upholding of democratic, constitutional, and legal principles in Pakistan and around the world”.

With inputs from AFP.