Washington  - President Barack Obama Wednesday signed into law a bill that will sharply increase health-care access for children, approving a long-time Democratic priority that Obama called a "downpayment" on wider health-care reform in the United States.

"Today ... we fulfill one of the highest responsibilities that we have - to ensure the health and wellbeing of our nation's children," Obama said in a signing ceremony at the White House.

The legislation adds 32.8 billion dollars over the next four-and- a-half years to the existing State Children's Health Insurance Program (SCHIP), allowing it to cover an extra 4 million children who don't have health insurance.

"I refuse to accept that millions of our children fail to reach their true potential because we fail to meet their basic needs," Obama said.

About 45 million people in the United States do not have health insurance, but how to reform the system is one of the most contentious and long-running disputes in US politics.

Obama called the SCHIP extension a "downpayment on my commitment to cover every single American."

The signing of the legislation follow's Tuesday's withdrawal of former senator Thomas Daschle as Obama's nominee for secretary of health and human service.

SCHIP currently covers about 7 million low-income children. With this bill, the programme is extended beyond March, when it was due to expire. The programme was created in 1997 under former president Bill Clinton.

The US House of Representatives passed the extension earlier Wednesday by 290-135 votes. The Senate approved it last week.

Former president George W Bush twice vetoed the programme's expansion, fearing it signalled a slippery slope toward a government takeover of health care. Obama promised during his presidential campaign to ensure all children would received health care. (dpa)