"We think that a political solution is the best way forward to denuclearize the Peninsula and to address North Korea's programs," Esper told reporters at Pentagon during a joint press conference with Chairman of the U.S. Joint Chiefs of Staff Mark Milley.
The Pentagon chief expected that the United States and the Democratic People's Republic of Korea (DPRK) could still pursue the diplomatic path over the nuclear issue.
"I remain hopeful that we could get the process started again," he said.
In the meantime, both Esper and Milley stressed that U.S. military forces are in a high state of readiness and "prepared to fight and win tonight if need be."
Pyongyang set its deadline for denuclearization negotiations at the end of this year, which was rejected by U.S. special representative for the DPRK Steven Biegun.
Biegun, who just has been confirmed as deputy secretary of state, said earlier this week in his meeting with South Korean President Moon Jae-in that the United States was unwavering in its efforts to denuclearize the Korean Peninsula via dialogue and diplomacy.
DPRK's Vice Foreign Minister Ri Thae Song warned early December that Washington would soon need to decide what kind of "Christmas gift" it will receive from Pyongyang.
The DPRK said it had carried out two "important tests" early this month. "I'd be disappointed if something would be in the works, and if it is we will take care of it," U.S. President Donald Trump told reporters Monday when asked about the latest developments in the DPRK.