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(CNN) —  

North Korea may be preparing to test engines and other components of its missile program, an administration official tells CNN, but senior military commanders said Friday that the US is ready for “whatever” Pyongyang might do.

Administration officials are closely monitoring satellite imagery for signs that North Korea may soon conduct a new round of weapons testing to deliver the “Christmas gift” that Pyongyang’s officials have promised the US if it doesn’t ease up on sanctions.

Due to North Korean measures to hide activities at several sites, the US cannot be certain what North Korean leader Kim Jong Un may order to be tested, one official said. One scenario suggests a test of a long-range missile or launch of a satellite on a long-range booster.

The Trump administration has been trying to negotiate with North Korea to have it dismantle its nuclear program, which poses a threat to US allies South Korea and Japan, and thousands of US troops based in both countries. Those talks have been stalled, even as Pyongyang has pursued technical improvements to its program that increasingly could put the US within range of its rockets.

Asked about recent comments and indicators from North Korea that Pyongyang may be getting closer to a long-range missile test or some other provocative act, Joint Chiefs Chairman Gen. Mark Milley said Friday that the Pentagon does not “discuss any intelligence or indicators” on what the US may be seeing in the way of preparations by North Korea.

’We are prepared’

He added, though, that through the public statements of its officials, “North Korea has indicated a variety of things … so we are prepared for whatever” Pyongyang may do.

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

If the US doesn’t ease sanctions, the North 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.

Pyongyang has already set a record for the number of missiles it launched this year, despite Trump’s boasts about his success in establishing a friendship with Kim. Over 2019, North Korea has also conducted 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 downplayed those tests, even as they have violated UN resolutions.

Hopes for diplomacy

Defense Secretary Mark Esper, speaking to the press Friday at the Pentagon alongside Milley, said he hopes that talks can be restarted and “that we could get the process started again and remain on the diplomatic path.”

Pyongyang, however marked the recent trip to the region by Steven Biegun, Trump’s special envoy for North Korea, by conducting “another crucial test” – its second in December.

“Clearly, we think a political solution is the best way forward to denuclearize the peninsula and to address North Korea’s programs,” Esper said on Friday. But he had started his remarks by noting that “we are in a high state of readiness, prepared to fight and win tonight if need be, and I am confident in that.”