Prime Minister Shinzo Abe and U.S. President Donald Trump agreed on Aug. 15 to cooperate with China and Russia to prevent North Korea from launching ballistic missiles toward Guam.

“The announcement of the plan to launch ballistic missiles at Guam has heightened tensions in the region to an unprecedented level,” Abe told reporters after his 30-minute telephone conversation with the U.S. president. “We were in agreement that the most important objective was to stop North Korea from going ahead with the missile launch by cooperating with the international community, including China and Russia.”

It was their first phone talks since July 31, when they held a discussion following a second launch of an intercontinental ballistic missile by North Korea.

Since that last call, tensions between the United States and North Korea have intensified, with Pyongyang’s announcement of the planned missile test over Japanese airspace and landing in waters off Guam and Trump’s statements indicating military action would be taken if North Korea goes ahead with the plan.

According to government officials, Abe and Trump also agreed that now was the time to implement tougher economic sanctions against North Korea, including a total export ban on its coal and seafood.

Abe also told reporters, “We will make every effort to prepare for any situation to protect the safety of the Japanese people through an advanced surveillance and missile defense structure based on a solid Japan-U.S. alliance.”

Japan has deployed Patriot Advanced Capability 3 (PAC-3) land-based interceptor missiles at four Ground Self-Defense Force bases in the prefectures of Shimane, Hiroshima, Ehime and Kochi to deal with the possible landing of North Korean missile parts on western Japan.