Washington (CNN) A top US military official in Asia said North Korea could launch a long-range missile as part of its promised "Christmas gift" to the US, a move that could ratchet up pressure on President Donald Trump as he enters his reelection year.

Gen. Charles Q. Brown, the commander of Pacific Air Forces, told a group of reporters in Washington on Tuesday that it was also possible North Korea could announce that its self-imposed moratorium on long-range testing was over without actually launching anything. Brown spoke at a Defense Writers Breakfast. CNN did not attend but confirmed his remarks with his spokesman.

Brown's assessment was based on open source rhetoric out of Pyongyang and not on an operational information or intelligence.

Brown said this was only one potential possibility, stressing that the US was still focused on diplomacy and nothing, in fact, might happen. But the new provocations from Pyongyang are raising concerns inside the White House that a period of relative calm is ending as Trump gears up for the 2020 campaign.

Tensions have ratcheted up as North Korea has conducted two new tests since the month began, declaring they were crucial for its nuclear program. It paired the tests with barbed insults about Trump ahead of a self-imposed end-of-year deadline for securing concessions from the United States.

An ominous pledge

If the US doesn't ease sanctions, North korea has promised the United States a "Christmas gift," an ominous pledge that could presage the resumption of long-range missile tests or a satellite launch, which Pyongyang had paused during bumpy attempts at diplomacy between the two countries.

A defense official told CNN that current information on the state of North Korean preparations indicates that Pyongyang is not moving to conduct an intercontinental ballistic missile launch before 2020. But that official said it is always possible for North Korea to ramp up preparations or launch something shorter range that requires less preparation.

A return to the contention that marked Trump's first year in office would undercut his boasts about avoiding war through three person-to-person meetings with leader Kim Jong Un. It would call into question his descriptions of a close friendship with the young despot, with whom he's exchanged "love letters" and briefly walked alongside into North Korean territory in June.

The meetings between the leaders did appear for a time to cause a cessation in the long-range missile launches and nuclear tests that led tensions to escalate in 2017. But Pyongyang steadily undercut Trump's claims of success by continuing to conduct tests, setting an all-time record for the number of missiles it launched this year.

Over 2019, North Korea has also done tests to improve technologies such as solid fuel, maneuverability, mobility and responsiveness that have implications for its ability to launch long-range systems, analysts say.

Trump has shrugged off the testing.

Now, though, Pyongyang's recent launches at a missile and satellite facility have led to concerns the country is heading toward resuming the program that once caused Trump to threaten to rain "fire and fury" on the regime.

There are also signs that global pressure on North Korea could be fracturing. This week, China and Russia proposed easing United Nations sanctions on the country, highlighting a divide in how best to prevent advances in its nuclear weapons program. The White House has said it's not considering easing any sanctions on North Korea.

The UN developments are feeding the concern among some of Trump's advisers that the relative calm that accompanied the diplomatic efforts could be ending, weakening Trump's political argument that he's brought about a new, more peaceful dynamic through his friendly overtures.

'A new way'

The three meetings between Kim and Trump, including Trump's historic stroll into North Korea with Kim in June, failed to yield discernible progress toward denuclearization, and the last attempt at working-level talks fell apart in October during a meeting in Stockholm, Sweden.

North Korea has warned it will resume its long-range tests if the US does not offer some concessions by the end of this year. Analysts say Pyongyang is frustrated by what it perceives as a lack of flexibility and creativity from US negotiators.

Some experts suggest Kim might face his own domestic pressures. "If Kim was only given rope internally until the end of the year to see if this dalliance with Trump yielded results, time may have run out for him and we may indeed get New Year's fireworks," said Vipin Narang, an associate professor at Massachusetts Institute of Technology. "And then instead of 'denuclearization' talks, we may see what 'renuclearization' looks like."

"It certainly sounds as if North Korea has made its strategic decision that talks with the US yielded no fruit, and that it will have to go a 'new way,' " Narang added.

Whatever Kim does next will be designed to capture Trump's attention.

North Korea's leader Kim Jong Un speaks as he stands with US President Donald Trump south of the Military Demarcation Line that divides North and South Korea, in the Joint Security Area (JSA) of Panmunjom in the Demilitarized zone (DMZ) on June 30, 2019.

An ICBM or a nuclear test would be provocative and would certainly achieve that goal, as would an attempt to use a rocket to launch a satellite into orbit.

"They have yet to demonstrate the ability to bring a large payload back into the Earth's atmosphere, a critically important requirement for their military ICBM program," said Evans Revere, a former Korea expert at the State Department.

Revere, who is a senior nonresident fellow at the Brookings Institution, said the international community shouldn't be surprised if this " 'satellite launch' includes a demonstration of their ability to send a major payload into the North Pacific."

That would convey to the US the "ominous message ... that the DPRK does indeed have the ability to strike the US homeland with a nuclear weapon," he said, using the initials for North Korea's official name, the Democratic People's Republic of Korea.

Trump has suggested that a major new missile test or satellite launch might be an attempt to manipulate election-year politics.

"He knows I have an election coming up. I don't think he wants to interfere with that, but we'll have to see," the President said earlier this month. "I think he'd like to see something happen. The relationship is very good, but there is some hostility, there's no question about it."

Increasing hostility

Since the start of this month, the hostility has increased. On December 2, North Korea warned it could resume long-distance missile tests in the next few weeks if the US does not change its negotiating position on the regime's nuclear disarmament.

Pyongyang wants the US to remove sanctions and provide security guarantees, saying, "It is entirely up to the US what Christmas gift it will select to get."

Three days later, a senior member of the North Korean government again described Trump as a "dotard" -- an insult implying senility -- after the US President revived his use of the name "Rocket Man" to describe Kim.

And this weekend, North Korean state media reported that a second "crucial test" had been successfully conducted this month at the country's Sohae Satellite launching ground, a site that the regime had begun dismantling during talks with the US. The week before, Pyongyang said a "very important test" had taken place at the same facility.

The Korean Central News Agency reported that the most recent test conducted at the satellite launching ground would bolster the country's "reliable strategic nuclear deterrent," a clear indication of the country's nuclear ambitions.

At the same time, Trump's special envoy for North Korea, Stephen Biegun, arrived in Seoul, South Korea, urging Pyongyang to return to nuclear talks.

"It is time for us to do our jobs. Let's get this done. We are here and you know how to reach us," Biegun said during consultations with his South Korean counterpart.

He said there is no deadline for the United States' negotiations with North Korea and that the two countries should aim to reach "balanced agreements."

"We are fully aware of the strong potential for North Korea to conduct a provocation in the days ahead. To say the least, such an action will be most unhelpful in achieving lasting peace on the Korean Peninsula. But it does not have to be this way. It is not yet too late," he said.

Defense Secretary Mark Esper said Monday that North Korea's rhetoric is a concern and tests "will be likely if they don't feel satisfied."

Trump himself said Monday that he is "watching" North Korea closely.

"We're watching it. We'll see. I'd be disappointed if something would be in the works, and if it is, we'll take care of it, but we'll see," Trump said during an event in the Cabinet Room. "We're watching it very closely."