Esper and South Korean Defense Minister Jeong Kyeong-doo announced the surprise decision during an impromptu joint press conference in Bangkok on the sidelines of a regional defense ministers' meeting led by the Association of Southeast Asian Nations.
"We have made this decision as an act of goodwill to contribute to an environment conducive to diplomacy and the advancement of peace," Esper said after announcing that the allies decided to postpone the Combined Flying Training Event set for later this month.
"We encourage the DPRK to demonstrate the same goodwill as the considerate decision on conduct of training, exercise and testing," he said, urging Pyongyang to "return to the negotiating table without precondition or hesitation."
DPRK stands for North Korea's official name, Democratic People's Republic of Korea.
The allies had planned to stage the joint air drills later this month, a scaled-back version of their original wintertime drills, codenamed Vigilant Ace, just as they did last year to support diplomacy with the North.
North Korea still angrily protested the upcoming drills, warning of "shocking punishment" that the US cannot cope with if the drills go ahead as planned.
"We have made this decision as an act of goodwill to contribute to an environment conducive to diplomacy and the advancement of peace," Esper said, adding, "We encourage the DPRK to demonstrate the same goodwill as the considerate decision on conduct of training, exercise and testing."
He then urged North Korea "to return to the negotiating table without precondition or hesitation."
Noting that diplomacy is the best way to achieve the complete denuclearization of the Korean Peninsula, the South Korean minister said that when to resume the postponed drills will be decided "through close coordination between the allies in accordance with how things are going down the road."
Seoul and Washington have canceled several combined exercises since last year in an effort to avoid provoking North Korea with maneuvers the communist regime has long condemned as a rehearsal for an invasion.
Stressing that the alliance between Seoul and Washington remains "ironclad" and their combined military forces "stand ready to fight tonight," the Pentagon chief pledged that the two sides "will continue to ensure our combined forces on the Korean Peninsula remain at a high state of readiness."
"Our willingness to modify training to keep the door open to an agreement on the denuclearization of the DPRK should not be mistaken for a lack of commitment to advance and defend our shared goals, interests and values." DPRK stands for the North's official name, the Democratic People's Republic of Korea.
"I don't see this as a concession. I see this as a good-faith effort by the United States and the Republic of Korea to enable peace and ... to facilitate a political agreement, a deal, if you will, for the denuclearization of the peninsula," Esper said, adding that his job is not only to foster diplomacy but also "to enable and empower it."
Nuclear talks between the US and the North have been stalled since February's summit between US President Donald Trump and North Korean leader Kim Jong-un fell apart due to differences over the scope of Pyongyang's denuclearization measures and Washington's sanctions relief.
The two sides held working-level talks last month, but no progress was made.
The North has given the US until the end of the year to put forward a new proposal that could break the deadlock in their nuclear talks, saying that otherwise, it would be compelled to give up on negotiations and choose to take a "new way."
Amid a lack of progress in the denuclearization talks, North Korea has carried out major weapons tests in succession this year, including new types of short-range ballistic missiles and a submarine-launched ballistic missile. (Yonhap)