KORUS is shorthand for the Korea-US free trade agreement that went into effect in 2012. Trump has slammed it as a bad deal that took away American jobs and widened the US trade deficit with South Korea. Negotiations to amend the agreement began in earnest this year and led to an "in principle" revision that is still subject to parliamentary ratification in both countries.

"A great deal for American and Korean workers," Trump said. "Let's now focus on our important security relationship."

The revision calls for further opening South Korea's auto market to the US, among other things, and comes with an agreement to exempt South Korea from new US tariffs on steel imports.

Instead, South Korea will face a quota on its steel exports to the US.

"This is a big deal for the American automotive industry," White House press secretary Sarah Sanders said at a regular news briefing later in the day. "It's a big deal for our parts manufacturers. It's a big deal for our pharmaceutical companies. And ultimately, it's a big deal and a major win for American workers and American businesses."

Responding to a question about whether an increased quota for US auto exports will actually increase sales to South Korea, Sanders said it's a step in the right direction that will help remove the US trade deficit. (Yonhap)