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By John Whitesides, Political Correspondent

WASHINGTON, Feb 11 (Reuters) - Democrat Barack Obama on Monday rode a weekend hot streak into the next round of presidential contests, but rival Hillary Clinton shrugged off the setbacks and expressed confidence about her prospects.

Obama is favored over Clinton on Tuesday in Virginia, Maryland and the District of Columbia, the latest battlegrounds in a tight back-and-forth struggle between the two candidates for the Democratic nomination in November's election.

At stake in Tuesday's voting are 168 pledged delegates to this summer's nominating conventions. Polls close at 7 p.m. EST/ (2400 GMT) in Virginia and at 8 p.m. EST/(0100 GMT on Wednesday) in Maryland and the District.

The two contenders crisscrossed the area around the nation's capital on Monday, hunting for support in a presidential race where momentum has been difficult to sustain.

Obama swept four contests over the weekend in the states of Maine, Louisiana, Nebraska and Washington, extending a slight lead in the battle for pledged delegates who select the nominee.

Obama, an Illinois senator, now has 943 pledged delegates to Clinton's 895, according to a count by MSNBC -- well short of the 2,025 needed to clinch the Democratic nomination.