Story highlights Hillary Clinton and Bernie Sanders met privately here on Tuesday evening

At stake in the primary are 20 delegates

Washington (CNN) Hillary Clinton and Bernie Sanders met privately at the Capital Hilton in Washington on Tuesday evening, just after Clinton won the final contest on the Democratic calendar in the District of Columbia.

The meeting came as the Vermont senator has begun signaling that his campaign is soon to close, though Sanders' aides say he is not expected to immediately endorse Clinton. Clinton became the presumptive Democratic presidential nominee, but Sanders declined to drop out and pledged to give every voter a chance to decide between the two candidates.

"Sen. Sanders and Secretary Clinton met in Washington on Tuesday evening and had a positive discussion about how best to bring more people into the political process and about the dangerous threat that Donald Trump poses to our nation," said Michael Briggs, Sanders' spokesman, in a statement. "Sanders congratulated Secretary Clinton on the campaign she has run and said he appreciated her strong commitment to stopping Trump in the general election."

Clinton and Sanders were joined by her campaign manager Robby Mook and campaign chairman John Podesta, along with Sanders' campaign manager Jeff Weaver and his wife, Jane. It lasted about 90 minutes.

The two were never alone in the room. Other lower level aides were in a nearby room and came in and out occasionally.

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