Seoul, South Korea -- South Korea and the U.S. are ending their massive springtime military drills as part of efforts to support diplomacy aimed at resolving the North Korean nuclear crisis. The Pentagon said in a release the U.S. and South Korean defense chiefs decided to conclude the Key Resolve and Foal Eagle series of exercises.

The decision will likely raise worries about how the allies will maintain their readiness in the event that military tensions erupt again in the wake of the recently failed summit between President Trump and North Korean leader Kim Jong Un.

The release said the allies agreed to maintain firm military readiness through newly designed command post exercises and revised field training programs.

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Smaller-scale drills will continue, but major planned war games will no longer go ahead, BBC News reported. North Korea, which views its nuclear weapons as key to its survival, has always regarded the games as preparation for a military invasion by the two countries.

Acting U.S. Secretary of Defense Patrick Shanahan and South Korean Defense Minister Jeong Kyeong-doo "made clear that the alliance decision to adapt our training program reflected our desire to reduce tension and support our diplomatic efforts to achieve complete denuclearization of the Korean Peninsula in a final, fully verified manner," the statement said.

Seoul's Defense Ministry released a similar statement.

After his second summit with Kim ended without any agreement in Hanoi on Thursday, Mr. Trump complained about the cost of annual military drills. "It's a very, very expensive thing and we do have to think about that, too," Mr. Trump said.

Following his first summit Kim in Singapore last June, Mr. Trump also suspended the allies' summertime military drills, calling them "very provocative" and "massively expensive." The U.S and South Korea also have suspended a few other smaller joint drills.

The Korean Peninsula remains in a technical state of war because the 1950-53 Korean War ended with an armistice, not a peace treaty. About 28,500 American soldiers are deployed in South Korea to deter potential aggression from North Korea.