The new bridge will be a little over a half-mile long, and its construction is expected to take 18 months, according to Russian state media. When the bridge is completed, it will help expand passenger and commercial traffic, as well as tourism, the North’s state media said. North Korea and Russia, whose relations had cooled in the post-Cold War decades, have reinvigorated their ties since 2023, when North Korea began supplying Russia with artillery shells, ballistic missiles and other conventional weapons to help aid its war against Ukraine. When Mr. Putin visited Pyongyang last June, the two countries signed a treaty on a comprehensive strategic partnership, which called for mutual defense and economic and other cooperation. During that visit, they agreed to construct a bridge for automobiles over the Tumen River, which runs along North Korea’s borders with Russia and China. Later last year, North Korea also began sending its troops to fight alongside Russian forces to help them retake territories lost to Ukraine in its Kursk region. On Monday, North Korea confirmed its troop deployment for the first time, and Mr. Putin formally thanked the country, promising not to forget the sacrifices of the North Korean soldiers.