U.S. President Donald Trump on Tuesday hinted at using his country's military might against North Korea if necessary, hours after the nuclear-armed nation again urged Washington not to ignore a year-end deadline for denuclearization negotiations set by Pyongyang.

Trump, however, emphasized his "good relationship" with North Korean leader Kim Jong Un, suggesting that the military option is not yet seriously on the table as the United States remains eager to continue talks with Pyongyang.

"Now we have the most powerful military we have ever had and we are by far the most powerful country in the world, and hopefully we do not have to use it. But if we do, we will use it. If we have to, we will do it," Trump told reporters in London.

But Trump, who is visiting the British capital to attend a summit of the North Atlantic Treaty Organization, added that he has "a very good personal relationship" with Kim. "I am possibly the only one he has that kind of relationship with in the world."

Trump's meeting with the press was livestreamed over the internet.

Earlier Tuesday, Pyongyang, via the state-run Korean Central News Agency, released a statement asking the United States to make concessions as the year-end deadline for progress in the talks looms.

"What is left to be done now is the U.S. option and it is entirely up to the U.S. what Christmas gift it will select to get," Ri Thae Song, vice foreign minister in charge of U.S. affairs, said in the statement in English.

"The DPRK has done its utmost with maximum perseverance not to backtrack from the important steps it has taken on its own initiative," Ri said, referring to the country by its formal name, the Democratic People's Republic of Korea.

Speculation has been growing that North Korea could launch a satellite or longer-range ballistic missile if the United States continues to show little sign of accepting demands by Pyongyang in the near future.

"The dialogue touted by the U.S. is, in essence, nothing but a foolish trick hatched to keep the DPRK bound to dialogue and use it in favor of the political situation and election in the U.S.," the vice minister said, citing next year's presidential election.

Trump, meanwhile, said in London, "My relationship with Kim Jong Un is really good, but that does not mean he will not abide by the agreement."

"You have to understand, go look at the first agreement we signed. It said he will denuclearize. That is what it said. I hope he lives up to the agreement but we are going to find out," he added.

At the first-ever U.S.-North Korea summit in June 2018 in Singapore, Trump promised to provide security guarantees to Pyongyang in return for "complete" denuclearization of the Korean Peninsula.

Nevertheless, North Korea has argued that the United States has not implemented the agreement despite Pyongyang taking what it says are concrete measures to discard its nuclear arsenal.

Pyongyang has called on Washington to abandon its "hostile policy" and stop making one-sided demands, if it wants to continue bilateral talks.

North Korea has recently warned that it may restart nuclear and intercontinental ballistic missile tests that could reach the United States, should negotiations over denuclearization fail to achieve a breakthrough by the end of this year.

Washington has still voiced willingness to maintain dialogue with Pyongyang, with U.S. special envoy for North Korea Stephen Biegun saying late last month that the "window for diplomacy" with the Asian country "remains open."

Since earlier this year, North Korea has carried out test-firings of what appeared to be short-range ballistic missiles in defiance of U.N. Security Council resolutions banning Pyongyang from developing ballistic missiles and nuclear weapons.

Late last week, KCNA reported that Kim oversaw the test-firing of a "super-large multiple launch rocket system" -- an action regarded as a provocation against the United States.

Washington and Pyongyang technically remain in a state of war after the 1950-1953 Korean War ended in a cease-fire. The two nations have no diplomatic relations.

In October, the two counties had a working-level meeting in the Swedish capital Stockholm, but North Korea has claimed that the talks broke down as the United States came to the table "empty-handed."

Related coverage:

Abe says summit with Moon being arranged in China in late Dec.

N. Korea suggests it may launch ballistic missile over Japan

Japan, India to conduct fighter jet drill for deeper security ties