They also say missile defense is too expensive to be America's primary strategy.
Mr Xi also stressed China and the USA shared "common interests" over denuclearisation and maintaining peace on the Korean peninsula.
While tensions typically spike around the dates of the exercises - North Korea conducted its fifth nuclear test just days after last year's manoeuvres - the situation generally calms afterward as the North needs to focus on its farms and the approach of the fall harvest.
"I will tell you this, North Korea better get their act together or they're going to be in trouble like few nations have ever been in trouble in this world, okay?" he added.
Missile tests by the North and impending military exercises by the South and the US have raised tensions on the Korean peninsula.
Friday: The US president warns that military solutions are "locked and loaded" should North Korea "act unwisely". "We will coordinate with the DND (Department of Defense), AFP, and relevant government agencies and meet necessary assessments in order to prepare appropriate contingency plans, alerts, and warnings for the awareness and protection of our civilian populists", he said. A USA defense official, who wanted to remain anonymous, said either an intermediate-range missile known as a KN-20 or a Hwasong-14, would "probably" be launched as it is the 64th anniversary of the signing of the Korean Armistice Agreement. "Hopefully Kim Jong Un will find another path!".
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Earlier, President Trump said the USA military was "locked and loaded" to deal with North Korea, should the need arise, as the countries' leaders increased bellicose rhetoric this week.
South Korea has almost 19,000 bomb shelters throughout the country but not many are aware of them despite growing North Korean threats.
To underscore the "locked and loaded" comment, Trump retweeted U.S. Pacific Command pictures of bombers on Guam.
The DPRK military said in a statement Thursday that its plan to strike Guam with intermediate missiles will be ready by mid-August and its implementation will depend on a decision by DPRK top leader Kim Jong Un.
So far, the language has only met with increasingly charged language from Pyongyang, which has threatened to attack Guam, the American territory in the Pacific that is home to a large military base. "He does something in Guam, it will be an event the likes of which nobody's seen before, what will happen in North Korea", Trump told reporters from the steps of his golf resort in Bedminster, N.J., on Thursday.
"While standing by 24 hours in preparation for a launch, we are calling on our residents to be on alert in case we issue emergency information", Makoto Ebuchi added. Judge Jeanine said. "We should have the ability to go after him first and block it".