The United States has told Japan it may resume large-scale joint military exercises with South Korea as early as next spring, if there continues to be no tangible progress on the denuclearization of North Korea, Japanese government sources said Monday.

Since September, the administration of President Donald Trump has communicated its plan to Japan a few times, according to the sources.

Japan, which has called on the international community to maintain pressure on Pyongyang, is supportive of the United States’ latest stance on the annual military drills, which Trump indefinitely suspended following his first-ever summit with North Korean leader Kim Jong Un, in mid-June in Singapore.

South Korea’s Defense Ministry has said it will decide whether to restart the joint drills by Dec. 1.

The Trump administration has touched on the possibility of resuming the two major spring exercises with South Korea known as Key Resolve and Foal Eagle, the sources said.

Key Resolve, a computerized command post exercise, was usually conducted between February and March, and Foal Eagle, a field training exercise involving ground, air and naval forces, typically took place between March and April.

Within the Japanese government, many believe that North Korea will not completely abandon its nuclear ambitions if the United States does not exert strong pressure on Pyongyang.

“Continuing to suspend the large-scale drills while there is no progress on U.S.-North Korea negotiations would benefit Pyongyang,” a senior Japanese diplomat said.

During a press conference after the historic summit with Kim on June 12, Trump said he will suspend “war games” with South Korea as long as North Korea engages in denuclearization talks in a sincere manner as they are “tremendously expensive” and “provocative.”

North Korea has for a long time slammed joint military exercises between the U.S. and South Korean forces as rehearsals for invasion, and regional tensions had escalated almost every year around spring.

The United States and South Korea have said the drills are defensive in nature.

Despite Kim’s pledge to work toward the “complete” denuclearization of the Korean Peninsula, Pyongyang has yet to take credible action to dismantle its weapons programs.

The United States and North Korea are still divided on ways to advance the denuclearization process.

U.S. Secretary of State Mike Pompeo’s planned meeting with his North Korean counterpart in New York last week was postponed at the last minute.

On Nov. 5, the U.S. and South Korean marines began a small-scale joint drill.

North Korea has already lashed out through its media at the U.S.-South Korean decision to resume the exercise, saying that it runs counter to recent efforts to lower tensions on the peninsula.