Obama poised to endorse Clinton, go after Trump

President Barack Obama is ready to make it official.

He's poised to formally endorse Democrat Hillary Clinton, his former secretary of state, and start aggressively making the case against Republican Donald Trump.

Clinton is on the verge of clinching the delegates required to win the party's presidential nomination.

White House officials say Obama's announcement could come within days, although not before Democrats in New Jersey, California and four other states vote Tuesday. The contests are expected to solidify Clinton's claim on the title of presumptive nominee.

The timeline is expected to hold regardless of how Clinton rival Sen. Bernie Sanders reacts to the Tuesday outcome, the White House said Monday.

White House and Clinton campaign aides have been discussing the sequencing of the long-expected announcement and Obama's schedule has several possible opportunities for maximizing its impact. On Wednesday, he's due in New York City to address donors at Democratic National Committee fundraiser in Clinton's home state. He'll also scheduled to tape an appearance on the "The Tonight Show Starring Jimmy Fallon," a favorite with the coveted young demographic, for the show set to air Thursday night.

The news will likely be followed up by a first joint appearance in coming weeks, said one official, who was not authorized to discuss plans before they were finalized.