WASHINGTON (NEXSTAR) -- U.S. leaders are concerned about evidence they say shows North Korea is sending troops to Russia, and the possibility that those soldiers could join the fight against Ukraine.  On Wednesday, the Biden administration said they have evidence that North Korea sent at least 3,000 troops to Russia this month. U.S. Defense Secretary Lloyd Austin says the Pentagon is working to gather more information.  "What exactly they're doing is left to be seen. These are things that we need to sort out," Austin said.  White House National Security Advisor John Kirby says they believe the soldiers are currently being trained in combat. He called it a "highly concerning probability" that those troops may be deployed to fight Ukraine alongside Russia.  "After completing training these soldiers could travel to Western Russia and then engage in combat against the Ukrainian military," Kirby said.  If that happens, Sec. Austin said it would be a problem with impacts on the conflict and more broadly in Europe and the Indo-Pacific region.  "That is a very very serious issue," Austin said. "You've seen DPRK provide arms and munitions to Russia, and, and this is a next step."  They warn that Russia's relationship with North Korea is dangerous, and say these actions violate multiple U.N. Security Council resolutions.  In response Kirby says the Biden administration is surging resources to Ukraine and is planning to sanction those enabling Russia's war.  "We recognize the potential danger here and we're going to be talking to allies and partners including the Ukrainians about what the proper next steps are going to be," Kirby said.  The officials also argue this shows Russian President Vladimir Putin is desperate for help.  "If Russia is indeed forced to turn to North Korea for manpower. This would be a sign of weakness, not strength on the part of the Kremlin," Kirby said.  "This is an indication that he may be even in more trouble than, than most people realize," Austin said.  The Chairman of the House Intelligence Committee says the U.S. may need to consider direct military action. Republican Congressman Mike Turner said in a statement, "If North Korean troops were to invade Ukraine's sovereign territory, the United States needs to seriously consider taking direct military action against the North Korean troops."