WASHINGTON—The United States on Wednesday imposed sanctions on six North Koreans, one Russian, and a Russian firm it said were responsible for procuring goods from Russia and China for North Korea’s weapons programs, an action that follows a series of North Korean missile launches, including two since last week. The U.S. Treasury said the steps aimed to prevent the advancement of North Korea’s weapons programs and impede its attempts to proliferate weapons technologies. The sanctions were the first specifically targeting North Korea’s weapons programs imposed by the Biden administration, which has sought unsuccessfully to engage Pyongyang in dialogue to persuade it to give up its nuclear bombs and missiles. U.S. State Department spokesman Ned Price said Washington remained committed to pursuing diplomacy with North Korea. “What we have seen in recent days … only underscores our belief that if we are going to make progress, that we will need to …