WASHINGTON — U.S. President Donald Trump on Thursday signed a national security memorandum permitting foreign shipbuilders to build up to two ships in their parent shipyards for delivery to the United States, as the U.S. seeks to rebuild its Navy and shipbuilding industrial base. The memorandum came as the U.S. is stepping up shipbuilding cooperation with Korea, which has committed to investing $150 billion in the U.S. shipbuilding sector as part of a total $350 billion investment pledge under last year's bilateral trade and investment deal. "As foreign shipbuilders make substantial and durable investments into America's shipyards and train an all-American workforce for the jobs they create, they will be temporarily permitted to build up to two ships in their parent shipyards that will be delivered to bridge gaps on a quick turnaround, while additional ships will be built in revitalized American shipyards," the White House said in a fact sheet. Under the memorandum, a foreign supplier subject to the memorandum is one that simultaneously builds a new shipyard in the U.S. or assumes own