ATLANTA (Reuters) - The head of the U.N. World Health Organization on Wednesday praised U.S. healthcare reforms signed by President Barack Obama this week as a breakthrough, stepping into a sharp domestic political debate.

“The people in this country and their leaders are courageous. That (healthcare reform) is an unprecedented achievement,” WHO Director General Margaret Chan said.

She was speaking to reporters after a lecture in which she argued that unrestricted market forces were limited as a means of redressing imbalances in global health care.

The reforms of the $2.5 trillion healthcare sector passed by Congress after months of heated debate will extend health insurance to 32 million Americans who currently have none.

It will also bar insurers from refusing coverage to people with preexisting medical conditions, expand the Medicaid government health insurance program for the poor and impose new taxes on the wealthy.

Conservatives and other critics argue that it will send the U.S. budget deficit soaring and slow economic recovery, but also that it represents unwarranted federal intrusion into the freedom of individuals to make healthcare choices.

Chan has made clear her view that governments and global organizations such as WHO should make a case for market regulation to deliver more equitable health benefits.

“Market forces, all by themselves, will not solve social problems. That is why public health needs to be concerned,” said Chan in a lecture at the U.S. Centers for Disease Control and Prevention.

“The hardest thing ... is persuading world leaders or ministers ... that health concerns can, in some instances, be more important than economic interests. Economic growth is not, after all, the be-all, end-all, cure-all,” said Chan, whose organization is based in Geneva.

She cited pharmaceutical companies which she said would not by themselves conduct costly research to deliver cheap drugs to combat preventable diseases that largely affect the poor.