Washington, July 23 - President Barack Obama has sought to sell his proposed healthcare reform as central to rebuilding the recession hit economy though he could not guarantee it won't change how Americans get medical treatment.

In a nationally televised news conference Wednesday dominated by the healthcare issue, Obama delivered lengthy statements in response to Republican attacks on proposals he favours, saying the change is necessary and good.

Repeatedly emphasising that the spiralling costs of the current system would bankrupt the nation while denying coverage to millions more Americans, Obama said: 'The whole point of this is to try to encourage what works.'

Addressing concerns that reform would take away the ability of people to choose their doctors and treatment, he said: 'The government is already making some of these decisions. Insurance companies are making some of these decisions.'

The reform proposals he backs would have experts make decisions based on the best medical treatment, not accountants attempting to save money or doctors prescribing treatments that bring the highest fees, Obama said.

Republican opponents of Democratic bills in the House and Senate said earlier that most Americans like the current system, which they said must be made less expensive and more accessible.