Prime Minister Margaret Thatcher displayed breezy confidence on the eve of a challenge to her leadership, saying in a newspaper interview published Monday that her work is unfinished "and it will be finished."

Thatcher will be in Paris for the 34-nation summit on European security when the result is announced Tuesday night of a vote on her leadership of the governing Conservative Party - and hence the government.The vote by the 372 Tory lawmakers in the House of Commons is routine each November under party rules. But this time Thatcher is being challenged by a strong candidate, former defense secretary Michael Heseltine.

With inflation and unemployment both rising, many Tories believe Thatcher, 65, has become too unpopular to win an unprecedented fourth term for the Conservatives in the next general election, due by mid-1992.

But before going to Paris, Thatcher told the Times of London: "It is one of my great accomplishments that we have restructured our industry, got rid of so much overmanning, got the framework of law pretty well right."

"It's not finished yet . . . and it will be finished," she said was quoted as saying. The Times said the prime minister "poured out a truly Wagnerian fury" at her challenger.