A Republican congressman, Thomas Massie, has introduced articles of impeachment against US Defence Secretary Pete Hegseth, accusing him of violating the constitution by engaging in hostilities against Iran for more than 90 days without congressional authorisation.

Massie said the move is intended to pressure President Donald Trump to replace Hegseth before Democrats take control of Congress in January and launch their own impeachment process.

However, Hegseth has dismissed the effort as a sham, insisting that he is not worried and remains committed to his responsibilities.

President Trump has also indicated support for the defence secretary.