The U.S. has canceled a massive joint air drill with South Korea dubbed "Vigilant Ace" that was scheduled for December this year.

After the ASEAN Defense Ministers' Meeting Plus in Singapore, U.S. Defense Secretary James Mattis and his South Korean counterpart Jeong Kyeong-doo agreed to suspend the drill to "give the diplomatic process" with North Korea "every opportunity to continue," a Pentagon spokeswoman said in a statement last Friday.

But the decision seems to have caught Seoul unawares, though it has been keen to foster rapprochement with North Korea in other ways and promote disarmament along the border.

A government official here said the U.S. does not want to deploy such a huge amount of military equipment at this time.

U.S. President Donald Trump has repeatedly decried the cost of the massive "war games" the two countries stage every year and offered at his summit with North Korean leader Kim Jong-un in May to suspend them because they are "very provocative."

"The final decision on the suspension of the drill will be made [between defense ministers] at the annual Korea-U.S. Security Consultative Meeting in Washington late this month," a ministry spokesman said.

"Korea will stage drills on its own anyway," he added.

