Seoul: US charges that North Korea helped Syria build a reactor are backing Pyongyang into a corner just as global powers are trying to force it to stop stalling on nuclear disarmament.

The United States released photographs on Thursday it said linked North Korea to a nuclear reactor under construction in Syria.

Japanese Prime Minister Yasuo Fukuda said possible North Korea-Syria cooperation could present major problems for preventing proliferation.

Under the deal North Korea struck with five regional powers, it had until the end of 2007 to disclose a complete list of its fissile material and nuclear weaponry.

If North Korea makes the declaration, the United States will remove it from a terrorism blacklist and allow Pyongyang to tap into international finance.