WASHINGTON (NEXSTAR) - Tuesday the Pentagon confirmed 10,000 North Korean troops are training in Russia and a “couple thousand” are already present in the Rusk region near the Ukraine border. Pentagon Press Secretary Air Force Major General Pat Ryder says the U.S. is closely monitoring the situation and is working with Ukraine and U.S. allies. "We remain concerned that Russia intends to use these soldiers in combat or to support combat operations against Ukrainian forces in Kursk." Major General Ryder says at this point there is no indication North Korean troops have crossed into Ukraine. President Joe Biden, who calls the situation “very dangerous,” told reporters if that line is crossed Ukraine should be able to strike. Ukrainian President Vladimir Zelensky says he expects the number of North Korean troops in Russia to grow to 12,000 “soon.” "So that's the first of course, is just escalation and how against sometimes I'm very surprised how, how our big partners, big strategic partners, said that we should not cross red lines and escalate, but we think that Russia does it itself," says Zelensky. Russian President Vladimir Putin is neither denying nor confirming the presence of North Korean troops in Russia.  Putin and North Korean President Kim Jong Un recently signed a treaty agreeing to support each other’s military capabilities. The pact requires either nation to immediately provide military assistance using “all means” if either is attacked. Secretary of State Antony Blinken and Defense Secretary Lloyd Austin are meeting with South Korean leaders in Washington this week.