Chinese and Russian intelligence-gathering ships have been sent out to track American aircraft carrier battle group heading for North Korea waters.

The dispatch of the spy vessels appears to be “partly aimed at sending a signal” the United States which has taken a tough stance against North Korea, according to the Japanese newspaper Yomiuri Shimbun.

UPDATE While earlier reports said that the USS Carl Vinson battle group was headed for the waters off North Korea, as of April 18th the aircraft carrier was believed to be thousands of miles away from the site. A report said the vessel left Singapore on April 8th and is expected to reach the Korean Peninsula by the end of the month.

“It appears that both countries aim to probe the movements of the United States, which is showing a stance of not excluding military action against North Korea,” the newspaper said. “The Self-Defense Forces are strengthening warning and surveillance activities in the waters and airspace around the area, according to the sources.”

By conducting joint exercises with the Maritime Self-Defense Force “and through other means,” the carrier group will pressure Pyongyang to “engage in restraint,” according to the newspaper.

Last week, U.S. President Donald Trump ordered the navy group led by the aircraft carrier USS Carl Vinson to enter the waters of the Korean Peninsula. The move was meant as a signal to the North Korean leader Kim Jong-un to back off from his recent missile launches and his nuclear arms program.

Concerns of a potential armed confrontation in the region have grown considerably higher with Pyongyang’s missile test launches and rhetoric from the American government. U.S. National Security Advisor Lt. Gen. H.R. McMaster said last week that “all options are on the table” including military intervention.

Beijing has warned that a conflict could break out “any moment” and called on heads of both countries to avoid an “irreversible route” which could lead to war, according to the Independent.

China appears to be the only country able to rein in the North Korean government, according to the Independent. In February, China stopped coal imports to North Korea to pressure the government. Last week, China deployed 150,000 along its border with North Korea.

Following the 105th anniversary of the birth of Kim Il-Sung, North Korea’s founding father, on April 15, North Korea will celebrate the 85th anniversary of the foundation of its military on April 25, according to the Yomiuri Shimbun.

Pyongyang, which has been conducting test launches of intercontinental ballistic missiles, intends to conduct its first nuclear missile test.