Florida Senator Marco Rubio said on Tuesday that he will not take shots at Donald Trump while refusing to offer a full-fledged endorsement of the presumptive Republican presidential nominee.

“My policy differences and reservations about Donald’s campaign are well established, and I stand by those. Those remain. And I hope they will be addressed. That said, I don’t view myself as a guy who’s going to sit here for the next six months taking shots at him,” Rubio said during as appearance at the Hudson Institute in Washington, D.C., on Tuesday.

“People know where I stand, they know how I feel, and they know what our differences are. He is the presumptive nominee of the Republican Party. I respect that and accept it. But that’s not going to change the reservations I have about his campaign or about some of the policies that he has established,” he added.

The former Republican presidential candidate said that he’s not insisting Trump change any of his policies because he will have the chance to make that argument to the American people. “I am going to focus on making the arguments I think are important for the country and right for our future,” Rubio said. “And I am looking forward to supporting candidates around the country, especially for federal office, that share those views.”

Rubio’s comments came days after House Speaker Paul Ryan said he cannot support Trump at this point.

Several former Rubio advisors and aides, including one of his main donors Paul Singer, have already announced they will not be supporting Trump in the general elections against Hillary Clinton.

But appearing on CNN’s “The Lead” on Tuesday, Rubio maintained that unlike Ryan, he signed a pledge to support the eventual Republican nominee. “I signed a pledge, put my name on it, and said I would support the Republican nominee and that’s what I intend to do,” Rubio said.

On Monday, Rubio also rejected to be considered as Trump’s running mate. While Republican voters have chosen Donald Trump as the presumptive GOP nominee, my previously stated reservations about his campaign and concerns with many of his policies remain unchanged,” Rubio stated in a message to his 1.4 million followers on Facebook. “He will be best served by a running mate and by surrogates who fully embrace his campaign. As such, I have never sought, will not seek and do not want to be considered for Vice President.“