China and Russia have agreed to take unspecified “countermeasures” in response to the planned U.S. deployment of an anti-missile system to South Korea — a move that came as Defense Minister Tomomi Inada inspected a version of the system on the U.S. territory of Guam on Friday.

The countermeasures in response to the U.S. deployment of the Terminal High Altitude Area Defense (THAAD) system will be “aimed at safeguarding interests of China and Russia and the strategic balance in the region,” China’s state-run Xinhua News Agency reported, quoting a statement released after a meeting of Russian and Chinese security officials.

“China and Russia urged the United States and South Korea to address their security concerns and stop the deployment of THAAD on the Korean Peninsula,” the statement read.

Washington and Seoul have pushed to send the THAAD system to the southeastern county of Seongju by the end of this year to counter growing nuclear and missile threats from North Korea, which unleashed a spate of missile tests and conducted two nuclear explosions last year.

Beijing and Moscow, however, have condemned the THAAD plan, saying the “missile defense system’s X-band radar can peer into territories of the two countries.” Media reports have also cited Chinese officials as saying that the true purpose for the deployment is to track missiles launched from China.

On Friday Inada toured Andersen Air Force Base in Guam, viewing the THAAD system there.

“We have no concrete plans to introduce THAAD, but we want to explore what is possible,” Inada was quoted by Kyodo News as saying.

The Defense Ministry reportedly included the costs of research into THAAD in its budget request for fiscal 2017, and Japan has been considering introducing the system as part of its multi-tiered ballistic missile defense program.

THAAD can cover a wider area because of its ability to intercept missiles at a higher altitude than the Air Self-Defense Force’s currently deployed surface-to-air Patriot Advanced Capability-3 (PAC-3) guided-missile systems.

The THAAD system is designed to intercept ballistic missiles flying at high altitudes in and outside the atmosphere, providing a longer-range defense than the PAC-3 system already deployed by the Self-Defense Forces. Reports have cited installation costs as running into the hundreds of billions of yen.

Under Japan’s missile defense program, Maritime Self-Defense Force Aegis destroyers are equipped with Standard Missile-3 interceptors which are intended to target and destroy missiles in the upper atmosphere. If they fail, the government claims the Air Self-Defense Force’s PAC-3 surface-to-air guided interceptors will be ready to shoot down the missiles.

As for the deployment of the THAAD system in South Korea, Seoul has recently complained that China appears to be tightening its economic vice on the country over the move. Experts say this, along with the joint Chinese-Russian statement, is likely an attempt by Beijing and Moscow to push Seoul to abolish the plan amid the uncertainty currently roiling the country in the wake of President Park Geun-hye’s impeachment and ensuing Constitutional Court proceedings.

“I think the joint statement is an attempt by Beijing and Moscow to shape the domestic opinion in South Korea toward rejecting the THAAD deployment,” said Tetsuo Kotani, a senior fellow at the Japan Institute of International Affairs in Tokyo.

“Even if the ROK rethinks the deployment, that would have less impact on Japanese consideration of the missile defense system,” he added, using the acronym for the Republic of Korea, the South’s official name.

Information from Kyodo added