Washington, Jun 6 (IANS): US Democratic front-runner Hillary Clinton was projected to win the Puerto Rico caucuses on Sunday night, leaving the former State of Secretary very close to secure her party's presidential nomination.

Clinton is not expected to win all 60 delegates that were at stake on Sunday, which would have put her over the top in the nomination battle against rival Bernie Sanders. She remains shy of the 2,383 she needs to win the Democratic nomination, CNN reported.

Clinton is closing in on a historic nomination as the first female presidential nominee with one more round of states -- California, New Jersey, New Mexico, South Dakota and Montana -- set to vote on Tuesday.

Her nomination would become official during the Democratic National Convention in Philadelphia.

She will become the first-ever female nominee of a major political party.

Her total delegate haul includes superdelegates, party officials who are unbound and can switch their support at any time.

Those superdelegates have overwhelmingly supported Clinton over Sanders, but could technically change their position.

Sanders has repeatedly said he will lobby them to do just that.

He said on Saturday that the Democratic convention would be contested. Asked by reporters on Sunday if that was still his position, he simply responded: "Absolutely."

Sanders even elevated his attacks on Clinton on CNN's "State of the Union," saying he is bothered by the potential conflict-of-interest of the Clinton Foundation's acceptance of gifts from foreign governments during her tenure as secretary of state.

He also cast Clinton as too hawkish, criticising her push to intervene in Libya, create a no-fly zone in Syria and vote to go to war in Iraq.

"I worry about that, yeah, I do. I think her support for the war in Iraq was not just an aberration," Sanders said.

For her part, Clinton is making a push for party unity -- and saying she expects Sanders to follow suit.

"After Tuesday, I'm going to do everything I can to reach out, to try to unify the Democratic Party, and I expect Sanders to do the same," Clinton said on Sunday.

"And we will come together and be prepared to go to the convention in a unified way, to make our case, to leave the convention, to go into the general election to defeat Donald Trump," Clinton said.