U.S. intelligence officials have developed evidence showing that North Korea is helping Syria to develop a nuclear program for weapons purposes, FOX News has learned in recent interviews with sources who have knowledge of the situation.

Syrians emphatically denied the claim on Thursday.

The details of the claims are vague, but one source told FOX News in late August that the North Koreans had sold the Syrians a nuclear facility, most likely related to uranium enrichment. Enriched uranium is necessary both for nuclear power and nuclear weapons uses. The United States accuses Syria of assisting terrorist groups including Hezbollah.

A source said the case has been assigned the internal code name, "Orchard," and the evidence was developed through Israeli channels, possibly with the assistance of U.S. aerial photography.

Other sources, however, questioned Syria's ability to afford such a pricey venture. Those sources said that in recent discussions with U.S. intelligence officials, the officials had spoken of North Korea having sent nuclear scientists, engineers, and other personnel with relevant expertise to Damascus.

"I've noticed more and more people [in the intelligence community] talking about people being sent over [from North Korea to Syria]," one high-ranking former National Security Council official said.

The former NSC official also said North Korea is "definitely still procuring [equipment] for its HEU [highly enriched uranium] program. It's not as if they are viewing the talks as some kind of 'time out' on their HEU work." This would be in direct contrast with efforts in the Six-Party talks to denuclearize the Korean peninsula .

Most of two dozen sources spoken to over the past three weeks, including current and former Bush administration officials, foreign diplomats, and nonproliferation experts, also said they have heard discussions about nuclear cooperation in one form or another between Syria and North Korea.

A spokesman for the Syrian embassy on Thursday called the allegations "absurd."

"This is an incredibly absurd and ridiculously fabricated story. Those who create such lies are misleading the American public and end-up undermining US national interest in a way reminiscent of what happened in Iraq previously. In fact, it is a shame that serious news outlets would waste time and space on such a fictitious idea," said embassy spokesman Ahmed Salkini.

James Rosen joined Fox News Channel (FNC) in 1999. He currently serves as the chief Washington correspondent and hosts the online show "The Foxhole." His latest book is "A Torch Kept Lit: Great Lives of the Twentieth Century" (Crown Forum, October 4, 2016).