In an exclusive interview with Xinhua, Eberhard Sandschneider, head of the German Council on Foreign Relations (DGAP) said sanctions "will not have any major impact" on the DPRK and will not help persuade the country to drop its plan to seek nuclear weapons.

"You can never force a country that won't cooperate into cooperation," said the German expert, adding that the rule also applies to Iran.

Sanctions won't work particularly on countries such as the DPRK, which is already very much isolated, he said.

Other forms of pressure were also unlikely to bring any positive results even backed by military threats, said Sandschneider, adding military strikes against the DPRK is not likely to happen as the United States is already over-stretched in Iraq.

The only way to solve the nuclear crisis remained "credible talks without any preconditions" and such talks should be initiated by the United States which the DPRK considered as its major threat, he said.

The DPRK is seeking nuclear weapons largely to prevent sanctions or strikes by the United States, he said.

DPRK's official Korean Central News Agency said Monday morning that the country had successfully conducted its first-ever underground nuclear test.