Washington (CNN) Maryland Sen. Barbara Mikulski, the longest-serving woman in the history of Congress, said that the Democratic primary ends in June, adding her voice to the growing calls in the party to unite behind one candidate ahead of the July convention.

In an interview with CNN, Mikulski was careful not to call on Sen. Bernie Sanders, who is trailing front-runner Hillary Clinton, to quit.

"I'm not one of those people (to say), 'Tell Bernie to get out,' " she said.

But she made clear that after the final votes are counted in June, the primary is "over," breaking with Sanders, who has vowed to take his fight to the July convention in Philadelphia.

"I'm a supporter of the full process playing out. I know it's hard. I know it's a slog ... but I want to be sure that all 50 states, territories, Democrats abroad -- that everybody has their say," said Mikulski, who supports Hillary Clinton. "So when we go to the convention, everybody's spoken. But when the process is over, through either primary or caucus, then it's over."

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