North Korea may be hoping to squeeze concessions from the international community by refusing to let inspectors remove samples from a plutonium-producing nuclear plant, the South's foreign minister said on Thursday. South Korea's top nuclear envoy was quoted as saying the move was effectively a rejection of a promise North Korea made last month to allow for checks of its nuclear claims. North Korea called the issue an infringement on its sovereignty, saying it was not part of a disarmament-for-aid deal struck with the United States, China, Japan, Russia and South Korea. "If we consider North Korea's clear negotiation pattern, its strategy has always been to create a crisis before resolving something, and trying to use that point to secure further concessions," Foreign Minister Yu Myung-hwan told a seminar.