Seoul, South Korea — Christmas day came and went with no sign of a "gift" from North Korea, CBS News' Barry Petersen reports. Pyongyang has warned of a possible surprise over the holidays if the United States does not ease sanctions before the end of the year.

Nuclear talks between the United States and North Korea have been stalled since a February summit between Mr. Trump and Kim Jong Un fell apart after the U.S. rejected North Korean demands for broad sanctions relief in exchange for a partial surrender of its nuclear capabilities.

There was speculation that the "gift" could be a test of a long-range intercontinental ballistic missile (ICBM) capable of delivering a nuclear warhead.

But on Tuesday, President Trump downplayed North Korea's warnings.

"Maybe it's a present where he sends me a beautiful vase as opposed to a missile test," Mr. Trump said.

The North Korean threat, even if it was just rhetoric, did spark action, however. On Wednesday, there were reports of four U.S. reconnaissance flights at the same time over the area — an unusually high number.

There were also satellite images of an engine testing area and signs of recent burns that could be from a new rocket engine.

This Dec. 19, 2019, satellite image from Planet Lab Inc., that's been analyzed by experts at the Middlebury Institute of International Studies shows the March 16 Factory in Pyongsong, near Pyongyang, where North Korea manufactures military trucks used as mobile launchers for long-range missiles. This new satellite image on a North Korean missile-related site shows the construction of a new structure this month. Planet Labs Inc., Middlebury Institute of International Studies via AP

But for the U.S. troops stationed in the region, Christmas brought dinner and presents from home.

"It's festive and you think of family and being separated from my wife is rough," Reginald Hill, from Arkansas, said.

Most American troops in South Korea are part of the Army's 2nd Infantry Division, whose motto is: "Ready to fight tonight." If there was ever a fight with North Korea, they are the Americans who would be first in harm's way.