The five-year, US$4.3 billion measure will provide medical treatment for emergency responders sickened by toxic dust inhaled at the World Trade Center site in New York in the days following the attacks.

It also includes a health program for responders sickened by the toxic debris and establishes a victims' compensation fund. Victims have five years to file claims.

Thousands of firefighters, police and other rescue and cleanup workers contracted respiratory problems and other illnesses from working at the World Trade Center site in the aftermath of the attacks.

"We will never forget the selfless courage demonstrated by the firefighters, police officers and first responders who risked their lives to save others," Obama said in a statement after the signing. "I believe this is a critical step for those who continue to bear the physical scars of those attacks."

Senator Kirsten Gillibrand of New York welcomed the move.

"Our nation -- Democrats, Republicans and Independents -- all came together to do what was right and provide healthcare to the brave men and women who served with such heroism in the days and weeks following 9/11," she said in a statement.

Obama is on vacation in Hawaii. He arrives back in Washington on Tuesday.