Sen. Joe Biden of Delaware.

WASHINGTON — Sen. Joe Biden of Delaware on Sunday became the fourth Democrat to formally announce plans to run for president next year.

"I am running for president," Biden said toward the end of an appearance on "Meet the Press" on NBC.

"I'm going to be Joe Biden, and I'm going to try to be the best Biden I can be," he said. "If I can, I got a shot. If I can't, I lose."

He said he would file paperwork by the end of the month to establish an exploratory committee to gather support for his bid.

Biden, who was first elected to the Senate in 1972, also sought the presidential nomination 1988. But he dropped out of the race after admitting that he had used speeches by other politicians without attribution, and after reports that he had plagiarized while in law school.

Biden, chairman of the Committee on Foreign Relations, joins a widening field of Democratic presidential hopefuls. The others who have officially announced their candidacies are former Sen. John Edwards of North Carolina, Rep. Dennis J. Kucinich of Ohio and Gov. Tom Vilsack of Iowa.

Other potential Democratic contenders for the White House include Sens. Hilary Rodham Clinton of New York and Barack Obama of Illinois. Among Republicans, Sen. John McCain of Arizona, former Gov. George E. Pataki of New York and Rudolph W. Giuliani, the former New York City mayor, are expected to run.