WASHINGTON - The US military has no plans yet to suspend any more major military exercises with South Korea, the defense secretary said on Tuesday, in the middle of a breakdown in diplomacy with North Korea over its nuclear weapons.Defense Secretary James Mattis told a Pentagon news conference that no decisions had been made about major exercises for next year, but noted that the suspension of drills this summer as a good-faith gesture to North Korea was not open-ended.US President Donald Trump's June decision to unilaterally suspend the drills caught many American military planners off guard and was broadly criticized as a premature concession to North Korean leader Kim Jong Un, who Trump wants to give up his nuclear weapons."We took the step to suspend several of the largest exercises as a good-faith measure coming out of the Singapore summit," Mattis told reporters, referring to the June 12 meeting between Trump and Kim."We have no plans at this time to suspend any more exercises," he said, adding that no decisions had yet been made on major exercises for next year.Mattis also said smaller exercises deemed to be exempt from the suspension were ongoing.Mattis' comments on the drills come at a delicate time for negotiations between the United States and North Korea after Trump scrapped plans for a meeting between top officials from both countries.At the June summit, the first meeting between a serving US president and a North Korean leader, Kim agreed in broad terms to work toward denuclearization of the Korean peninsula. But North Korea has given no indication it is willing to give up its weapons unilaterally as the Trump administration has demanded.Since then, diplomats have failed to advance the process.North Korean officials even warned in a letter to U.S Secretary of State Mike Pompeo last week that denuclearization talks risked falling apart, US officials told Reuters.In particular, the North wants steps toward a peace treaty. The 1950-1953 Korean War ended in an armistice rather than a peace treaty, leaving US-led U.N. forces technically still at war with North Korea.US officials fear North Korea might turn its attention to cutting a separate deal with South Korea and driving a wedge between the US-South Korea alliance.A South Korea presidential spokesman acknowledged that talks between Washington and Pyongyang were at a stalemate."With North Korea and the U.S. remaining stalemated, there is an even bigger need for an inter-Korea summit," Kim Eui-kyeom, a spokesman for the presidential Blue House, told a briefing.South Korean President Moon Jae-in said this month his planned third summit with North Korea's Kim next month would be another step toward the denuclearization of the Korean peninsula and an end to the Korean War.