U.S. Sen. Elizabeth Warren, D-Mass., endorsed Hillary Clinton for president Thursday, sending a message to supporters of U.S. Sen. Bernie Sanders of Vermont that it’s time to rally against presumptive Republican candidate Donald Trump.

The endorsement came hours after President Barack Obama and Vice President Joe Biden also announced their support for Clinton.

Warren had been the holdout among the Senate’s Democratic women as she waited until Clinton gained the number of delegates needed to secure the nomination next month in Philadelphia, which she did this week.

Elizabeth Warren Endorses Hillary Clinton Sen. Elizabeth Warren, D-Mass., addresses the American Constitution Society's convention on Thursday, June 9, 2016. The senator attended the group's gala dinner at the Capital Hilton in Washington. Photo: Astrid Riecken/Getty Images

“I’m ready to get into this fight to make Hillary Clinton the president of the United States and be sure that Donald Trump gets nowhere near the White House,” Warren said on MSNBC’s “Rachel Maddow Show” Thursday evening. She praised Sanders' campaign for inspiring millions, but stated that “Hillary Clinton won. She’s a fighter. She’s out there. She’s tough.”

Warren said she has not been approached by Clinton as a potential running mate. “I know there’s been a lot of speculation, but I love the work that I do.”

She continued her attack on Trump she started earlier in the day, calling him a “small insecure bully” and “a genuine threat to this country.”

“There is an ugly side to Donald Trump, and we have to make she he doesn’t come within shouting distance of the White House,” Warren said. “He was rooting for an economic crash, because he could make money at it.”

Earlier Thursday, Warren went on the offensive against Trump during a speech in Washington at the American Constitution Society of Law and Policy's 2016 convention, roasting him as a “loud, nasty, thin-skinned fraud.”

Trump “has never risked anything for anyone and serves nobody but himself. And that is just one of the many reasons why he will never be president,” Warren said, at one point mocking Senate Majority Leader Mitch McConnell, R-Ky., and other Senate Republican leaders, whom she blamed for Trump’s rise to power.

Biden followed Warren to the podium at the event in D.C.,  speaking of the need to fill the Supreme Court seat vacated by the death of conservative Justice Antonin Scalia earlier this year. During his remarks he said since the Senate refuses to vote on Obama's nominee, Judge Merrick Garland, the seat will be filled by the next president: “God willing, it’ll be Secretary Clinton.”