WASHINGTON — The Democratic Party on Monday approved Puerto Rico's proposal to scrap its caucus and hold a presidential primary on June 1.

A primary will give more voters a chance to take part in the nominating process, said Puerto Rico Democratic Chairman Roberto Prats. He said caucuses were fine in previous years, when the party nominee was settled by the time Puerto Rico voted and the only task was to choose delegates to the national convention.

"Now it's different," Prats told the Democratic National Committee's rules panel in a conference call. "This is the first time in decades that Puerto Rico will be participating in an event of this magnitude."

Democratic Sens. Barack Obama and Hillary Rodham Clinton are locked in a historic fight for the nomination that could last all the way to the national convention this summer in Denver. Puerto Rico will have 55 delegates at stake in its primary, and will award them proportionally.

Only three remaining states, Pennsylvania, North Carolina and Indiana, have more Democratic delegates up for grabs.

Obama leads in the race for the nomination, with 1,620 delegates, including endorsements by superdelegates, the elected and party leaders who automatically attend the convention. Clinton has 1,499 delegates, according to the latest tally by The Associated Press.

Clinton's campaign announced Monday that her husband, former President Clinton, will campaign for her in Puerto Rico early next month.

Prats said Puerto Rican supporters of both candidates backed the primary.

Puerto Rico's original plan called for selecting delegates at caucuses June 7. However, after the DNC approved the plan in December, it was discovered that the date was typo and should have read June 1, DNC officials said.

The new date means Montana and South Dakota will hold the party's last nominating contests, on June 3.