Defense Minister Itsunori Onodera said Thursday he was briefed from his U.S. counterpart that the United States is making arrangements with South Korea about joint military drills, which U.S. President Donald Trump vowed to halt.

Onodera told reporters that he also affirmed with U.S. Defense Secretary Jim Mattis the close alliance of the two countries during their phone talks, which followed the historic summit between Trump and North Korean leader Kim Jong Un in Singapore.

Japan has welcomed the fact that Trump and Kim agreed to work toward North Korea's complete denuclearization, but has expressed concerns over Trump's suggestion made after the summit to suspend U.S.-South Korean joint military exercises.

For U.S. allies Japan and South Korea, military exercises conducted with the United States have been perceived as sending out deterrent messages to the region and used as a tool to pressure North Korea into giving up its nuclear arms and missile ambitions.

During the phone talks with Mattis, Onodera also said he underscored the importance of the presence of the U.S. military in South Korea for security in East Asia.

Mattis assured that the United States is not considering the reduction of its troops in South Korea, which remains technically at war with the North since the 1950-1953 Korean War ended in an armistice, not a peace treaty.

Onodera and Mattis also agreed to carry out joint exercises between Japanese defense forces and the U.S. military as they have done before.