(Updates with trade deal, share movement)
SEOUL, March 26 (Reuters) - South Korea's steelmakers rose on Monday, with market heavyweight Posco leading the overall sector after the United States agreed to exempt South Korea from its new steel tariffs.
Washington will impose a quota on steel imports instead, while South Korea in return will improve access for U.S. automakers under the bilateral free trade deal known as KORUS.
Shares in sector heavyweight Posco added 2.0 percent, while Dongbu Steel gained 6.9 percent. Husteel shares rose 3.4 percent, while Seah Steel and Seah Besteel gained 2 percent and 4.9 percent respectively.
The sub-index for iron, steel and metal rose 1.7 percent, edging back from earlier gains, ahead of a 0.8 percent gain in the broader market.
Auto shares were mixed, with Hyundai Motor 1.3 percent weaker and Kia Motors up 0.5 percent.
Under KORUS revisions, U.S. automakers will be able to bring into South Korea 50,000 vehicles per automaker per year that meet U.S. safety standards, not necessarily Korean standards, up from 25,000 vehicles previously.
South Korea and the United States earlier this month held a third round of negotiations on revising their trade pact. Reducing South Korean non-tariff barriers to U.S. automotive exports has been a priority for the Trump administration.
Trump late on Thursday issued a proclamation that South Korea, Argentina, Australia, Brazil and the European Union would get temporary exemptions from steel and aluminum tariffs, along with Canada and Mexico's earlier exemptions. The exemptions run until May 1 as discussions continue. (Reporting by Dahee Kim and Hyunjoo Jin; editing by Richard Pullin)