WASHINGTON (Reuters) - The U.S. Secret Service said on Monday it would participate fully in probes announced by President Joe Biden and members of Congress, after its agents failed to prevent a gunman from shooting and injuring former President Donald Trump over the weekend.

The FBI says it is investigating the incident on Saturday at a Trump rally in Pennsylvania as an assassination attempt. Biden said on Sunday he had ordered an independent review, and Republican lawmakers vowed swift investigations.

In her first major statement since the shooting, which killed a rally attendee, Secret Service Director Kimberly Cheatle said the agency was increasing security for Republican presidential candidate Trump and the Republican National Convention in Milwaukee, which kicks off on Monday.

"I am confident in the security plan our Secret Service RNC coordinator and our partners have put in place, which we have reviewed and strengthened in the wake of Saturday's shooting," Cheatle said in a statement.

She said the agency has implemented changes to Trump's security detail since Saturday to ensure his protection during the convention and the remainder of the campaign.

Trump said a bullet grazed his ear during the Saturday rally but that he is doing fine. He traveled to Milwaukee on Sunday and is expected to receive his party's formal nomination later this week.

(Reporting by Susan Heavey; additional reporting by Katharine Jackson; editing by Rami Ayyub)