Margaret Thatcher's campaign to remain Britain's prime minister received a jolt Friday when her foreign secretary hinted he might join the leadership battle.

But the minister, Douglas Hurd, stressed he would not challenge Thatcher directly.Hurd, 60, has formally proposed Thatcher's candidacy for a ruling Conservative Party leadership ballot Tuesday in which she is opposed by former Defense Minister Michael Heseltine.

He told a news conference in the northern city of Leeds he believed Thatcher would win on the first ballot.

However, he said in a reply to a question that there were no circumstances under which he would run against Thatcher - raising the possibility that he might be a candidate if she dropped from the race to head the Conservative Party.

Some commentators said Hurd appeared to have stopped short of total endorsement for Thatcher to continue her fight to the end should she fail to score a commanding victory in the first round.

Heseltine seized on Hurd's remark. He told British Broadcasting Corp. radio: "If people think that Douglas will be a better leader than myself, they have to vote for me in the first round."