SEOUL, South Korea (AP) – Intelligence officials reported increased activity Tuesday around North Korea’s main nuclear reactor, indicating the country may be preparing to uphold its agreement to shut down the plant.

North Korea missed last Saturday’s deadline for shuttering the reactor because of a dispute over North Korean deposits frozen in a bank blacklisted by Washington.

The country promised America and four other nations in February to dismantle its nuclear programs in return for energy aid and political concessions.

North Korea successfully tested a nuclear bomb in October and is believed to have produced as many as a dozen atomic bombs since it kicked out U.N. nuclear inspectors and quit the Nuclear Nonproliferation Treaty late in 2002.

South Korea’s main spy agency was “following and analyzing some peculiar movements” around the reactor, an official at the National Intelligence Service told The Associated Press. The official declined to be named, citing policy.

South Korea’s Yonhap news agency said it was highly possible the activity was preparations for a shutdown. Yonhap cited an unnamed intelligence official as saying the activity has increased in the last week or so and consisted of more than just cars and people moving around the site. The reactor remained in operation Tuesday.

The South Korean newspaper Dong-a Ilbo carried a similar report.

Pyongyang had said that its pledge was contingent on the release of money frozen in a separate financial dispute after Washington blacklisted a bank where North Korea had accounts. The funds were allegedly used in money laundering and counterfeiting.

The money was freed for withdrawal last week, but it’s unclear when the North will move to get its $25 million.

South Korean Foreign Minister Song Min-soon spoke by telephone Tuesday with his American counterpart, Condoleezza Rice, and the two “strongly expressed expectations that North Korea will soon implement disarmament measures,” the Foreign Ministry said in a statement.

Mr. Song and Ms. Rice “reaffirmed that the door to resolving the (bank) issue is clearly open to North Korea and agreed to continue discussions among related countries to resolve the issue,” the statement said.

China said Tuesday that it hoped the bank dispute would be resolved and progress made on disarming the North.

“We look forward to and welcome the continuing constructive efforts from all parties concerned to jointly promote the process” of disarmament talks among the two Koreas, China, Japan, Russia and the U.S., Foreign Ministry spokesman Qin Gang said in a statement on the ministry Web site.