Ukraine has been hit by a surge in Russian ballistic missile attacks, about a third of which used North Korean weapons that can only fly because they run on Western circuitry, obtained despite sanctions,

The U.S., South Korea and others say North Korea has sent more than 10,000 troops to Russia to support its war against Ukraine.

WASHINGTON, Nov 21 (Reuters) - President Joe Biden dropped his opposition to Ukraine firing U.S. missiles at targets deep inside Russia in response to North Korea's entry to the war, a shift in U.S. policy that took on added urgency following Donald Trump's Nov. 5 election win, sources familiar with the matter said.