SEOUL (Reuters) -South Korea's chief presidential policy adviser said on Thursday he was "optimistic" about ongoing talks to finalise a trade deal with the U.S., in the latest remarks by officials suggesting progress in negotiations that had stalled for months.

Kim Yong-beom and Industry Minister Kim Jung-kwan spoke to reporters before departing for the United States. They will be joining Finance Minister Koo Yun-cheol and Minister for Trade Yeo Han-koo for follow-up negotiations in Washington.

Kim's comments echo Minister Koo's remarks earlier this week that there was "huge progress" and Foreign Minister Cho Hyun saying there were "positive signals" in reaching a deal.

On the U.S. side, Treasury Secretary Scott Bessent said on Wednesday the countries were close to finalising a trade deal and he expected an announcement in the next 10 days. Seoul has been seeking to reach a deal by late October when U.S. President Donald Trump is due to visit the country for an Asia-Pacific summit.

South Korea agreed in late July a preliminary deal with Trump lowering U.S. tariffs on imports to 15% from 25%, in return for South Korean investment of $350 billion in U.S. strategic industrial sectors.

A promised cut in U.S. tariffs on auto imports to 15% from 25%, however, has not been implemented for South Korea amid stalled negotiations over the details of the investment package, while rival Japan secured this last month after finalising its deal including $550 billion investments in the U.S.

Seoul has been concerned over the foreign exchange implications and the structure of the investment package and asked Washington for a safeguard, such as a currency swap line, to prevent any currency market impact.

South Korea's benchmark KOSPI stock index rose as much as 1.9% to a record high on Thursday, as shares of Hyundai Motor ( HYMLF ) surged 9.6% to a one-year high and sister automaker Kia jumped 8%.