South Korean trade officials braved snowstorms, ate instant noodles to save time and spent weeks hotel-hopping in Washington as they raced to overcome major trade hurdles with their U.S. ally ahead of high-stakes nuclear discussions with North Korea.

What was meant to be a weeklong trip to Washington stretched into a four-week marathon, as dozens of Seoul officials sought to wrap up talks aimed at amending the six-year-old U.S.-Korea Free Trade Agreement known as KORUS, according to several South Korean officials with direct knowledge of the matter.

U.S. plans announced earlier this month to impose hefty tariffs on steel and aluminum imports added urgency to the trade negotiations. As the third-largest steel exporter to the United States, South Korea had a lot to lose from 25 percent tariffs.