(USA TODAY) - North Korean leader Kim Jong Un will watch what "the foolish Yankees" do before making a decision on plans to fire four missiles toward the U.S. territory of Guam, state media in the reclusive nation reported.

Kim was briefed on and examined the plan, and said he would watch Washington’s actions “a little more,” the official Korean Central News Agency reported, according to the South Korean news agency Yonhap.

Kim said he will make an “important” decision if Washington continues its "extremely dangerous reckless actions,” Yonhap reported.

"In order to defuse the tension and prevent dangerous military conflict on the Korean Peninsula, it is necessary for the U.S. to make a proper option first and show it through action," he said.

Yonhap reported that Kim made the comments Monday while inspecting the Strategic Force command, which last week threatened to launch the intermediate-range ballistic missiles toward the western Pacific island.

"If they fire at the United States, it could escalate into war very quickly," U.S. Defense Secretary Jim Mattis told reporters Monday.

Mattis said the U.S. will know a missile’s trajectory “within moments” and "we will take it out" if it heads toward U.S. territory.

Earlier Monday, Marine Corps Gen. Joseph Dunford, the U.S. military’s most senior officer, warned on a visit to South Korea that the United States is ready to use the “full range” of its military capabilities to defend itself and its allies against North Korea.

The office of South Korean President Moon Jae-in said Dunford, the chairman of the Joint Chiefs of Staff, said military options would be used if diplomatic and economic sanctions fail.

China, North Korea's most important ally, said Monday that it will stop importing North Korean goods including iron ore, coal and fish from midnight on Sept. 5. as part of U.N. sanctions imposed on Pyongyang over its nuclear and missile program.

The U.N. Security Council imposed increased sanctions on North Korea worth one-third of its annual $3 billion exports earlier this month.

President Trump warned last week that the U.S. military is "locked and loaded" should North Korea "act unwisely." National security adviser H.R. McMaster said the president’s statement was an effort to maintain peace, not provoke war.

North and South Korea are celebrating Liberation Day on Tuesday, marking the anniversary of the victory over Japan in World War II and the creation of the two independent Korean governments in 1948.