President Joe Biden and South Korean President Yoon Suk Yeol are set to sign an agreement including plans to have U.S. nuclear-armed submarines dock in South Korea for the first time in more than 40 years. That's according to three senior Biden administration officials who briefed reporters on the conspicuous show of support to Seoul amid growing worry about North Korean nuclear threats. Wednesday's announcement of the dock visits is a key element of what’s called the “Washington Declaration,” aimed at deterring North Korea from attacking its neighbor. The agreement also seeks to ward off South Korea from restarting its own nuclear program. The declaration is being unveiled as Biden hosts Yoon for a state visit.