The Republican frontrunner to be the new speaker of the US House of Representatives, Kevin McCarthy, abruptly dropped out of the race Thursday, lawmakers said, amid a revolt by the party's hard-line conservatives.

McCarthy, currently the party's number two in the House behind outgoing speaker John Boehner, had appeared to have the backing of most of the chamber's Republican lawmakers for the top job in Congress.

"He said he didn't think he is the right man to be the face of the party," congressman Walter Jones told reporters as he left a party conference meeting where Republicans were expected to nominate McCarthy.

House leadership announced a postponement of the party election for speaker until a later date.