By Ian Simpson

WASHINGTON (Reuters) - Attorneys for Roger Clemens and the government are expected to make opening arguments on Monday in a new trial of the former baseball pitching ace, who is accused of lying to Congress about taking performance-enhancing steroids.

The two sides were in the final steps of selecting the 12-member jury and four alternates, concluding a process that began a week ago, roughly nine months after his first trial was halted due to a misstep by prosecutors.

Clemens sat forward in his chair with his back to spectators and said nothing as his attorneys also presented two preliminary motions to U.S. District Court Judge Reggie Walton.

Walton declined to rule immediately on either motion - one questioning whether former teammate Andy Pettitte can testify about where Pettitte got steroids and another questioning whether Congress should have called Clemens to appear before it in the first place.

Initial statements were expected in the early afternoon, and the case is expected to run for up to six weeks.

The seven-time Cy Young Award winner was indicted in 2010 for perjury and obstruction over 2008 testimony to Congress in which he denied taking steroids and human growth hormones. U.S. prosecutors say they have evidence to the contrary, and will seek to discredit him.

Clemens' first trial began in July 2011, but Walton declared a mistrial after two days when prosecutors showed jurors a video clip that included material the judge had banned from the case unless the information was raised by Clemens' defense team.

Walton agreed to a new trial after prosecutors said the error in the first attempt was not intentional.

The allegations that Clemens, 49, used performance-enhancing drugs has raised questions about his record. Known as "The Rocket," Clemens played for four teams over a 24-year career and his seven Cy Young wins for best pitcher in his league are a record.

Clemens is one of the biggest names linked to steroid use in baseball. Other stars who have faced questions about doping include sluggers Mark McGwire and Jason Giambi and home-run king Barry Bonds.

(Reporting by Ian Simpson; Editing by Jackie Frank)