North Korea may be preparing to shut down its main nuclear reactor, news reports said Tuesday, renewing hopes that Pyongyang will comply with a disarmament agreement days after it missed a deadline to shutter the facility.

The Yongbyon reactor was still in operation, but there was a high possibility that movement of cars and people at the site recorded in satellite photos could be linked to a shutdown, South Korea's Yonhap news agency reported, citing an unnamed intelligence official. The Dong-a Ilbo daily carried a similar report.

An official at the National Intelligence Service, South Korea's main spy agency, told The Associated Press they were "following and analyzing some peculiar movements" around the reactor in North Korea, without elaborating. The official spoke on condition of anonymity, citing policy.

Yonhap news agency cited another unnamed intelligence official as saying that South Korea and the United States have been closely monitoring some movement since a month ago.

"The intensity of these activities has increased from about a week or two ago," the official was quoted as saying. "There are activities other than cars and people moving busily."

The report comes after the North missed a Saturday deadline to shut down the reactor and allow U.N. inspectors to verify and seal the facility under a February agreement with the U.S. and four other countries.

If the North complies, that would be its first move toward stopping production of nuclear weapons since 2002, the start of the latest nuclear standoff. The North is believed to have produced as many as a dozen atomic bombs since then, and conducted an underground test detonation in October.

Pyongyang said last week that honoring 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 U.S. counterpart, Condoleezza Rice, and the two "strongly expressed expectations that North Korea will soon implement disarmament measures," the Foreign Ministry said in a statement.

Song and 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.

Macau's Banco Delta Asia said Monday it had filed a legal challenge to Washington's decision to cut it off from the U.S. financial system. The bank told the U.S. Department of Treasury that its accusations "lacked specific facts" and were motivated by politics, the bank said in a statement.

The U.S. move was "politically motivated since it was based on disputes between the United States and North Korea." The bank has repeatedly denied knowingly helping in North Korea's alleged illicit activities.

In Washington, the U.S. Treasury Department expressed confidence it would ultimately prevail in the legal challenge.

"The Treasury Department has confidence in the merits of its action against Banco Delta Asia, as demonstrated by the information put forth in the final rule," which cuts the bank off from the U.S. financial system, said department spokeswoman Molly Millerwise.

Meanwhile, there have been reports that South Korea was considering suspending rice shipments to the North in an apparent to move to ratchet up pressure.

The two Koreas were set to begin talks Wednesday in Pyongyang to discuss the North's request for 400,000 tons of rice.

South Korea periodically sends rice and fertilizer to the impoverished North, which has relied heavily on foreign handouts since the mid-1990s when natural disasters and mismanagement devastated its economy and famine led to the deaths of as many as 2 million people.