North Korea faces another round of sanctions for staging a nuclear test, but more punitive measures may not go far against an impoverished regime with little left to lose.

The potency of possible new restrictions is a wild card in the efforts of the U.N. Security Council, the United States and its allies to contain North Korea's nuclear ambitions and coax it back to negotiations.

International sanctions are "not effective at all," said Paik Hak-soon, a North Korea analyst at the Sejong Institute outside Seoul. "North Korea has already tested the bomb and has long expected this response."

The United States, Japan and others have slapped a series of sanctions on Pyongyang over its nuclear program in recent years. And the countries had indicated that similar consequences would be in store over a nuclear test, long before Monday's still unconfirmed detonation.

Actions already taken range from blacklisting North Korean banks and restricting port entry of its ships to backing a global ban on trading some military technology with the North. After the crackdown, trade with Japan alone tumbled 85 percent, to a paltry $195 million last year, from 2001.

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Yet North Korea went ahead and tested anyway.

"The truth is, there is little that Washington or Tokyo can do, politically or financially, that has not already been done," Ralph Cossa, president of the Honolulu-based Pacific Forum, wrote in a report on the standoff.

North Korea also has scoffed at more sanctions.

"We have lost enough," a North Korean official in Beijing was quoted as saying by South Korea's Yonhap news agency. "Sanctions can never be a solution."

But increasing sanctions may be all that's left. Military action or a strategic airstrike against North Korea is riskier than ever in the face of atomic retaliation.

Tougher measures hinge on whether China and Russia — the North's closest allies — support them. South Korea, which has long pursued a policy of engagement with its neighbor to ease tensions, is also a weak link, cautious not to spoil hard-won goodwill with its former enemy and further upset regional stability.

Measures under consideration at the United Nations include international inspection of all cargo to and from North Korea to limit the proliferation of nuclear, chemical and biological weapons, and blanket bans on luxury and military goods and any material that could be used in the production of weapons of mass destruction.

A U.S. draft resolution contains tough new proposals from Japan to ban all countries from allowing in North Korean ships or aircraft carrying arms, nuclear or ballistic missile-related material or luxury goods.

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The Japanese proposals also would impose travel restrictions on high-ranking North Korean officials and create a Security Council committee to monitor implementation of sanctions.

The U.N. Security Council can authorize a range of measures under Chapter 7, from breaking diplomatic ties and imposing economic and military sanctions to taking military action to restore peace.

In 2000, the United States eased a blanket ban on U.S. exports to North Korea dating to 1950 in an effort to improve relations. Reinstating the ban remains an option.

Legitimate trade has fueled modest North Korean economic growth in recent years after a dismal 1990s.

Trade with China has climbed for five consecutive years, doubling over the period to $1.58 billion, according to the most recent figures from South Korea's Unification Ministry. Commerce with the South more than doubled, to $1.05 billion.

So effective sanctions are also risky, posing the danger of triggering a collapse of North Korea's teetering economy.

"If the North is further weakened there is a possibility that the North could destabilize and use the military option as a stopgap measure to maintain control," said Michael Williams, head of the trans-Atlantic program at the Royal United Services Institute, a defense think tank. "In many senses it is preferable to have a strong state in control of nuclear weapons, because at least there is some hierarchy and structure."