WASHINGTON - PRESIDENT Barack Obama and South Korean President Lee Myung-bak on Tuesday forged a united front against North Korea, saying the hermit nation must abandon its nuclear weapons program and will not be rewarded for provoking a crisis.

'There's been a pattern in the past where North Korea behaves in a belligerent fashion and if it waits long enough is then rewarded with food stuffs and fuel and concessionary loans and a whole range of benefits,' Mr Obama said.