South Korea's top official on North Korea stressed Monday that delivery of promised rice aid to Pyongyang depends on whether the communist nation lives up to its commitment to start dismantling its nuclear weapons program. At talks between the two Koreas that ended Sunday, the South agreed to send 400,000 tons of rice to the North despite its failure to meet a deadline more than two weeks ago to shut down its main nuclear reactor. The text of the agreement contains no preconditions for the aid delivery that is to begin in late May. However, Unification Minister Lee Jae-joung said Monday that South Korea has "strongly delivered" its position that delivery of rice aid depends on whether North Korea implements the February accord reached at international arms talks. Under the accord, North Korea was to shut down its Yongbyon reactor by April 14 and allow UN inspectors to verify and seal the facility in exchange for energy assistance. "The rice issue is not just a humanitarian issue, but a very symbolic and essential task for peace ... so I believe it is very important that measures under the (February) agreement are implemented," Lee told MBC radio. The two Koreas also agreed Sunday to conduct test runs of trains on rebuilt tracks across their shared border on May 17. A planned test run was called off last year because the North Korean military refused to guarantee the safety of travelers during the test. "This is one of the tasks that has to be solved through dialogue with the (North Korean) military," Lee said. "If (the test run) is canceled again this time, it will bring difficulties to fundamental South-North relations." South Korea remains technically at war with the North since the 1950-53 Korean War ended in a cease-fire, not a peace treaty. However, in the past decade, Seoul has tried to reconcile with its former wartime foe - lavishing aid on the North and sometimes playing a middleman between Pyongyang and Washington at nuclear arms negotiations. But South Korea's conservative Grand National Party said Monday that the government's decision to send rice to the North was another example of "one-sided giving." "Boundless leniency toward North Korea, which ignores international practice, will only result in being a poison to South-North relations," party spokeswoman Na Kyung-won told reporters. Another Grand National Party lawmaker claimed Monday that the South Korean government estimates it would take up to 15 years for the North to completely dismantle its nuclear program. "Time is on North Korea's side," Chung Hyung-keun said in comments posted on the party Web site, referring to the North's track record of stalling at disarmament negotiations to win concessions. North Korea has refused to move on disarmament because of a delay in getting funds frozen in a Macau bank after it was blacklisted by the United States for allegedly assisting the North with money laundering and counterfeiting. The US$25 million has been freed for withdrawal, but for unknown reasons the North has not yet moved to remove the money. In an attempt to resolve the impasse, South Korea's chief negotiator to nuclear talks, Chun Yung-woo, left for Washington Monday to discuss the issue with his US counterparts. "We can't keep putting off discussions on denuclearization that are more important because of the (bank) issue," Chun said before departure, South Korea's Yonhap news agency reported. Chun said they had "a general understanding of North Korea's demands" regarding its money, without elaborating, according to the report. The nuclear talks also involve China, Japan and Russia.