NEW YORK (CBSNewYork) — Bernie Sanders will finally give his stamp of approval to Hillary Clinton.

CBS News chief White House correspondent Major Garrett reported the Vermont senator will endorse Clinton next Tuesday in New Hampshire and bring the Democratic Party together before Donald Trump and Republicans meet for their convention.

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Garrett told WCBS 880 the presumptive Democratic presidential nominee would have preferred the endorsement sooner but the campaigns are organizing it in a way to build sense of unity and momentum to counteract Trump and the Republicans a week before the Republican National Convention.

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“Bernie Sanders will make it clear that he is not only with Clinton, but diametrically opposed to Trump,” Garrett explained.

Garrett reported Sanders was able to get concessions, including a significant policy one when Clinton expanded her push for college tuition subsidies earlier this week, bringing it to a nearly universal subsidized college tuition plan Sanders pushed for.

Garrett also reported Sanders was getting word from Democrats that he was taking too long to endorse Clinton, and that he needed to get on board and unify the party “because Trump is the overriding existential threat to the Obama agenda and everything the Democrats accomplished the last eight years.”

Sanders told PBS’ “Charlie Rose” show that Clinton needs to be elected president.

“We have got to do everything that we can to defeat Donald Trump and elect Hillary Clinton,” Sanders said. “I don’t honestly know how we would survive four years of a Donald Trump” as president.

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Despite the upcoming endorsement, Sanders still has yet to officially drop out of the race.