Japan has resumed negotiations with North Korea on the abductees issue, but further missile tests by Pyongyang could undermine Tokyo’s assurances that the process will not impair coordinated action with the U.S. and South Korea to curb the North’s weapons programs.

Washington and Seoul have expressed support for Tokyo’s push to resolve Pyongyang’s abduction of Japanese nationals in the 1970s and 1980s as a humanitarian issue. But it is unknown whether they will back Japan’s negotiations with North Korea if the country takes increasingly provocative steps, such as launching a long-range ballistic missile that could hit the United States, or conducting a fourth nuclear test.

After Japan eased its sanctions on July 4 in return for launching a new round of investigations on the abductee issue, Pyongyang has fired short-range ballistic missiles in violation of U.N. Security Council resolutions.

Defying international objections, North Korea’s official media on Thursday mentioned the possibility of conducting more missile launches and a nuclear test as “self-defense” measures against U.S.-South Korea joint military exercises.

The United States and South Korea are concerned that Japan may lift more of its unilateral sanctions against North Korea, depending on the progress of the investigations, fearing that such an approach could diminish international pressure on the North to give up its missile and nuclear weapons programs.

To allay these concerns, Foreign Minister Fumio Kishida told U.S. Secretary of State John Kerry and South Korean Foreign Minister Yun Byung-se in a meeting Sunday in the Myanmar capital of Naypyitaw that Japan will ensure transparency in its dealing with Pyongyang.

Experts argue that while the abductees issue is a bilateral matter between Tokyo and Pyongyang, it is important that Japan promote information sharing and hold close consultations with the United States.

“If Japan fails to share information and sufficiently consult with the United States, Japan-North Korea relations would be out of step with a broader picture of international politics,” said Koji Murata, president of Doshisha University and a specialist in U.S. foreign policy and international security.

Similarly, a group of U.S. and Japanese experts and former policymakers, including former Deputy Secretary of State Richard Armitage and former Deputy Secretary of Defense John Hamre, said in a July 14 report that there must be “no surprises” in the Japan-U.S. relationship.

The account reflects U.S. vigilance amid speculation that Prime Minister Shinzo Abe may visit North Korea for a summit with leader Kim Jong Un — just as former Prime Minister Junichiro Koizumi traveled to Pyongyang in 2002 for talks with Kim Jong Il that led to the return of five abductees — without sufficiently consulting Washington beforehand.

Despite calls for cooperation between Japan, the U.S., South Korea and other members of the international community to keep North Korea in check, Pyongyang is unlikely to stop developing missiles capable of carrying nuclear weapons that can strike as far away as the United States.

Missiles are among the reclusive country’s key exports, especially to the Middle East, and missile tests represent Pyongyang’s attempt to attract potential buyers and draw more foreign currency, according to experts on North Korea.

“With or without Japan’s engagement, North Korea is likely to continue launching missiles and conducting nuclear tests,” said Korean affairs expert Hideshi Takesada, citing Pyongyang’s policy of promoting economic construction and nuclear development simultaneously.

North Korea revised its constitution in 2012 to proclaim itself a nuclear state in the face of what it terms a “U.S. nuclear threat.”

“North Korea has claimed that as Pyongyang aims to unify the Korean Peninsula, it will continue developing nuclear weapons to block U.S. military intervention,” said Takesada, a professor at the Graduate School of International Cooperation Studies at Takushoku University. “The simultaneous pursuit of economic development includes improved ties with Japan.”

In such circumstances, Takesada recommended that the United States and South Korea, along with China and Russia, increase efforts to resume the six-party talks aimed at ending North Korea’s nuclear ambitions, so they can better assist Japan’s initiatives on the abductees issue.

Underscoring concerns about Pyongyang’s weapons development, a U.S. institute said July 29 that fresh satellite images suggest North Korea may be wrapping up engine trials on an intercontinental ballistic missile “by the end of this year,” raising speculation of about an upcoming flight test.

“If the engine tests are concluded, the next stage in development of the KN-08 road-mobile ICBM may be full-scale tests of the missile,” the U.S.-Korea Institute at Johns Hopkins University says on its 38 North website.