WASHINGTON, May 1 (Reuters) - The U.S. Department of Justice said on Sunday that Halliburton Co and Baker Hughes Inc had abandoned their planned merger, which the agency filed suit in April to block.

"The companies' decision to abandon this transaction - which would have left many oilfield service markets in the hands of a duopoly - is a victory for the U.S. economy and for all Americans," Attorney General Loretta Lynch said in a statement.

(Reporting by Peter Cooney; Editing by Andrew Hay)