An obscure banking inquiry has hijacked a landmark nuclear disarmament deal with North Korea, to the surprise and dismay of U.S. and some foreign officials who have tried for months to resolve the mess.

To try to salvage the nuclear pact, Washington first truncated and then throttled back a Treasury Department inquiry related to alleged money-laundering sanctioned by the North Korean government. Ultimately, the Bush administration agreed to help hand over money it had earlier identified as tainted.