The United States Attorney in the nation's capital indicted Roger Clemens on Thursday, an event that puts the 48-year-old Texan, one of the greatest pitchers in baseball history, on the precipice of becoming the first Major League Baseball star to face prison time for his role in the steroid era.

A seven-time Cy Young Award-winner who helped the Yankees to two World Series championships, Clemens was charged with one count of obstruction of Congress, three counts of making false statements and two counts of perjury for his testimony during a 2008 congressional probe into the disputed findings of former Senator George Mitchell's report on steroid and human growth hormone use in baseball.

Clemens faces up to 30 years in prison and a $1.5 million fine if convicted of all the charges, although he would probably serve 15 to 21 months in prison under federal sentencing guidelines.

His case is before Judge Reggie Walton, who presided over the perjury conviction of former Vice-President Dick Chaney's chief of staff, Scooter Libby, and he is expected to be arraigned within two weeks.

"Our government cannot function if witnesses are not held accountable for false statements made before Congress," said United States Attorney Ronald Machen. "Today the message is clear: If a witness makes a choice to ignore his or her obligation to testify honestly, there will be consequences."

Clemens continued to deny the allegations, responding to the charges Thursday afternoon via Twitter.

"I never took HGH or Steroids. And I did not lie to Congress," Clemens Tweeted Thursday afternoon. "I look forward to challenging the Governments accusations, and hope people will keep an open mind until trial. I appreciate all the support I have been getting. I am happy to finally have my day in court. Rocket"

Clemens' lawyer, Rusty Hardin, said in a press conference in his Houston office late Thursday afternoon that the government had made Clemens the offer of a plea bargain but that he had rejected it.

"Roger has known from the very beginning that if he chose to deny the accusations in the Mitchell Report, this day would come," Hardin said. "Hopefully we haven't reached a stage in this country where you have to admit something you didn't do."

Hardin then said Clemens "is as upbeat as he had ever been," but that the former Yankee pitcher would "withdraw from the media after this."

Clemens and his former trainer, Brian McNamee, testified under oath in a contentious hearing before the House Committee on Oversight and Government Reform in February of 2008. McNamee, who cooperated with federal authorities and with baseball's Mitchell report on performance-enhancing drugs in baseball after being threatened with prosecution, said Clemens had used steroids and human growth hormone, while Clemens denied having ever used the substances.