U.S. President Barack Obama has signed the country's sweeping healthcare reform legislation.

U.S. President Barack Obama (C) signs the healthcare reform bill at the White House in Washington D.C., capital of the United States, March 23, 2010. [Xinhua]

The 938-billion-US-dollar health care overhaul will bring the most profound changes to the nation's social security system in more than four decades.

Tuesday's signing was more than celebration.

It capped a year-long struggle to pass the historic legislation that will help define Barack Obama's presidency.