WASHINGTON — In negotiations that went right to the deadline, No. 1 overall draft pick Stephen Strasburg and the Washington Nationals agreed tonight to a record-breaking contract worth about $15 million over four years.

"He's chomping at the bit to get out on the mound. He's ultra-, ultra-competitive," acting Nationals general manager Mike Rizzo said, "and I think he was getting a little tired of sitting around the house."

The San Diego State pitcher's deal is worth roughly 50 percent more than the previous highest guaranteed deal for a player in baseball's amateur draft, the $10.5 million Mark Prior got from the Chicago Cubs in 2001.

"We thought we signed the player for his value," Rizzo said, calling Strasburg "the most coveted amateur player in the history of the draft and a potential front-line starting pitcher."

The last-place team and the hard-throwing right-hander faced a deadline of midnight on Monday night to come to an agreement. And, according to Nationals president Stan Kasten, they resolved everything without much time to spare — "11:58 and 43 seconds," he said.

"People thought it would take to the last minute," Kasten said, smiling. "We didn't even need that last minute."

Strasburg gets a four-year contract covering 2009-12 that will pay him slightly more than $15.1 million. The exact amount depends on prorating his $400,000 salary for this year, based on the date the contract is official.

If no agreement had been reached by the deadline, the team would have relinquished its rights to Strasburg. A year ago, Washington failed to reach an agreement with its first-round selection, Missouri pitcher Aaron Crow.

At 6-foot-4, 220 pounds, and with a fastball that can reach 100 mph, Strasburg is projected to be precisely the sort of ace the Nationals have lacked since moving from Montreal to the nation's capital before the 2005 season.

He went 13-1 last season, leading Division I pitchers in ERA (1.35) and strikeouts (195 in 109 innings), and won the Golden Spikes award for the top U.S. amateur baseball player.

In part because of a lackluster starting rotation, Washington is on pace for a second consecutive 100-loss season.

The expectation is that Strasburg will join third baseman Ryan Zimmerman as one of the primary faces of a franchise that is heading to its fourth last-place NL East finish in five seasons.

In many ways, the Nationals needed to sign Strasburg — and not just because of what he offers as a pitcher. That is certainly important, of course, particularly when you consider that the five pitchers currently holding spots in Washington's starting rotation are a combined 16-23 with a 4.52 ERA this season.

The Nationals also hope Strasburg can help boost interest in the team. Since opening their $600 million-plus stadium for the 2008 season, the Nationals have struggled to attract fans: They are averaging about 23,100 spectators this season, worse than all but two NL clubs.

Whatever the PR benefit to the signing, the Nationals are most excited about his pitching talent.

"He's got the skill set that all front-of-the-rotation starting pitchers have. He's a big, physical guy. He throws extremely hard. He's got a solid repertoire of pitches and he throws them all for strikes," Rizzo said.

"Barring injury," the acting GM added, "this kid should have a long, illustrious career."

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AP Baseball Writer Ronald Blum in New York contributed to this report.