Trump said at the meeting that he has yet to attack Flake hard, but threatened to begin doing so.

Flake stood up to Trump by urging him to stop attacking Mexicans. Trump predicted that Flake would lose his reelection, at which point Flake informed Trump that he was not on the ballot this year, said the sources, who spoke only on the condition of anonymity because they were not authorized to disclose details of the private meeting.

Flake’s spokesman did not immediately reply to a request for comment.

Trump also called out Sen. Mark Kirk (R-Ill.), who withdrew his endorsement of Trump last month citing the business mogul’s racially-based attacks on a federal judge, and said he did not approve of the senator’s action, said the officials.

Characterizing Kirk as a loser, Trump vowed that he would carry Illinois in the general election even though the state traditionally has been solidly Democratic in presidential contests. Kirk did not attend the meeting with Trump.