May 1 (Reuters) - Halliburton Co and Baker Hughes Inc are expected to announce the termination of their merger agreement on Monday after it faced opposition from U.S. and European antitrust regulators, a person familiar with the matter said.

The contract governing Halliburton's acquisition of Baker Hughes, which was valued at $35 billion when it was announced in November 2014, expired on Saturday without an agreement by the companies to extend it, the person added.

The source asked not to be identified because no official announcement has yet been made. Halliburton and Baker Hughes did not immediately respond to requests for comment.

(Reporting by Mike Stone in New York; Editing by Andrew Hay)