U.S. Senator Mikulski, Maryland Democrat, to retire: media

U.S. Senator Barbara Mikulski (D-MD) rides an escalator into the subway system at the U.S. Capitol in Washington, January 16, 2014. REUTERS/Jonathan Ernst

WASHINGTON (Reuters) - U.S. Senator Barbara Mikulski of Maryland, the top Democrat on the powerful Appropriations Committee and the longest-serving female senator, is set to announce that she is retiring, according to media reports. Mikulski, 78, scheduled a news conference on Monday at 11 a.m. EST in Baltimore to make an announcement about her future, her office said. Mikulski has served in the Senate since 1987 and before that in the U.S. House of Representatives. The Baltimore native earned a reputation for toughness and fiery outspokenness during her five terms in Washington. She is considered one of the more liberal members of Congress and opposed the invasion of Iraq. She also defended government spending in an era of austerity, saying in 2012 that Congress could be "frugal without being heartless." That year, NASA researchers in Baltimore discovered the glimmer of an exploding star, which they named "Supernova Mikulski" after the senator. (Reporting by Emily Stephenson; Editing by Bill Trott)