US President Barack Obama says his embattled signature healthcare programme is "here to stay" after more than 7 million Americans signed up.

He told reporters the law, nicknamed Obamacare, represented progress and benefitted the economy. Mr Obama also lashed out at repeated conservative efforts to repeal or defund the law, calling it "troubling". There would be additional challenges to implementing the law, he said, but it was "working". An estimated 7.1 million Americans signed up for coverage to avoid penalties prior to Monday's deadline for doing so, exceeding initial projections. "This law has made our healthcare system a lot better," Mr Obama said at the White House on Tuesday, adding that it would lower overall healthcare costs. Though the reform had at times been "contentious and confusing", he said, "that's part of what change looks like in a democracy. "Change is hard. Fixing what is broken is hard." Controversial law State and federally-run marketplace websites allow residents to choose between several private insurance options The Democrat leader has battled political opposition to Obamacare - officially the Patient Protection and Affordable Care Act - for years. Republicans - who see it as an inappropriate government intrusion into the healthcare industry and an affront to personal liberty - are not expected to relent in their opposition to the law. The law also remains controversial among the American public, as some people have seen their insurance costs rise or their old plans cancelled, and others object to having to purchase insurance at all. The Republicans hope to tap into voter discontent with the law in November's midterm elections. The 2010 law is intended to extend health insurance to the roughly 48 million Americans who do not receive it through their employers, the government, or a privately purchased plan. It also aims to slow the growth in the cost of healthcare and requires private plans to meet a certain level of coverage. The federal Healthcare.gov and similar marketplace websites run by some states are a key element of the law, providing a clearing-house for people to purchase health insurance for themselves and their families, often with generous subsidies.