WHITE HOUSE - North Korea appears to have a placed a device in a tunnel at its nuclear test site that could be detonated Saturday or even sooner, U.S. government and other sources said Wednesday.

"U.S. intelligence is always on alert for a possible North Korean weapons test," a U.S. Intelligence official told VOA on Thursday "Kim Jong Un wants his country to be validated as a nuclear power and a test would further that goal."

North Korea on Saturday will observe the "Day of the Sun," marking the 105th birth anniversary of its founder, Kim Il Sung.

Commercial satellite imagery of the Punggye-ri Nuclear Test Site from Wednesday showed continued activity around the north portal, new activity in the main administrative area and a few personnel around the command center, according to the 38 North website, which is run by the U.S.-Korea Institute of the School of Advanced International Studies at Johns Hopkins University.

Punggye-ri, North Korea nuclear test site Punggye-ri, North Korea nuclear test site Punggye-ri, North Korea nuclear test site

The nuclear test facility is "primed and ready" for what would be North Korea's sixth nuclear test, according to an analysis by Joseph Bermudez Jr. and Jack Liu.

South Korea has no indications a military provocation by the North is imminent, Joint Chiefs of Staff spokesman Roh Jae-chun told reporters in Seoul on Thursday morning.

Conversation with Xi

U.S. President Donald Trump, at a news conference Wednesday with visiting NATO Secretary General Jens Stoltenberg, said he had spoken with China President Xi Jinping the previous evening and "I think he wants to help us with North Korea." If that does not occur, "we're just going to go it alone."

Trump echoes that sentiment on Twitter Wednesday morning

I have great confidence that China will properly deal with North Korea. If they are unable to do so, the U.S., with its allies, will! U.S.A. — Donald J. Trump (@realDonaldTrump) April 13, 2017

Xi told Trump that China believes the issue of North Korea's intercontinental ballistic missile and nuclear weapons development should be resolved through peaceful means, according to Chinese media reports.

A U.S. naval strike group, led by the USS Carl Vinson aircraft carrier, following a regularly scheduled assignment in Singapore, was ordered to head north "as a prudent measure" instead of heading toward Australia, as had been planned.

Officials of the Pacific Command told VOA the new position of the vessels off the Korean Peninsula would come at a time when the "number one threat in the region continues to be North Korea, due to its reckless, irresponsible and destabilizing programs of missile tests and pursuit of a nuclear weapons capability."

The carrier strike group, according to sources, includes the USS Ohio submarine, armed with 154 Tomahawk cruise missiles.

'An armada'

"We are sending an armada. Very powerful," Trump told the Fox Business Network on Tuesday. "We have submarines. Very powerful. Far more powerful than the aircraft carrier."

The major ships that comprise the strike group acc The major ships that comprise the strike group accompanying the aircraft carrier U.S.S. Carl Vinson to the waters off South (and North) Korea. The major ships that comprise the strike group accompanying the aircraft carrier U.S.S. Carl Vinson to the waters off South (and North) Korea.

In an interview with The Wall Street Journal on Wednesday, Trump, speaking about North Korea, said "you cannot allow a country like that to have nuclear power, nuclear weapons. That's mass destruction."

The president added that North Korean leader Kim Jong Un, the grandson of Kim Il Sung, "doesn't have the delivery systems yet, but he will. In many ways, that's the easiest thing."

There is also speculation that North Korea could imminently test-fire another intermediate- or long-range ballistic missile, tied to the upcoming holiday.

In April 2012, North Korea tried to launch a long-range rocket ahead of Kim Il Sung's 100th birth anniversary.

That launch failed.