South Korea's Presidential Office said on Tuesday the country's national interests are more important than rushing into negotiations with the United States, after US President Donald Trump announced 25 percent tariffs on imports from South Korea starting August 1.

Relevant ministries need to "make utmost efforts on negotiations with the US by putting national interests at the top priority", Kim Yong-beom, the presidential chief of staff for policy, was quoted as saying by the Yonhap News Agency.

Kim was speaking at a meeting with relevant ministries that was called following the publication of a letter from Trump addressed to South Korean President Lee Jae-myung.

"Starting on August 1, 2025, we will charge Korea a tariff of only 25 percent on any and all (South) Korean products sent into the United States, separate from all sectoral tariffs. Goods transshipped to evade a higher tariff will be subject to that higher tariff," Trump said in the letter posted on his Truth Social platform.

He told reporters later that the date of Aug 1 is not 100 percent firm as he hinted at the possibility of delay on implementation depending on trading partners' proposals.

Trump initially announced 25 percent levies on South Korea in April, which were originally due to take effect on July 9 after a 90-day pause for negotiation.

As South Korea has just went through a presidential transition triggered by the impeachment of former president Yoon Suk-yeol over his botched imposition of martial law in December, the country has yet to finalize a trade agreement with the US.

Though the new government has made all-out efforts to reach a mutually beneficial resolution with the US since Lee took office on June 4, Kim said there was insufficient time to reach an agreement given the complexity of the issue.

South Korea's National Security Adviser Wi Sung-lac travelled to the US on Sunday to hold talks with his US counterparts on a wide range of issues, including trade and a possible summit between the respective leaders.

Wi will return to South Korea on Wednesday, according to the country's presidential office. He will then hold a joint meeting with the Presidential Policy Office and the National Security Office to review the situation and discuss future responses.

South Korea's exports to the US could contract substantially in the second half of 2025 if the US tariff policy is implemented in earnest, said Chang Sang-sik, head of the Korea International Trade Association's International Trade and Commerce Research Center.

At a forum in Seoul hosted by the Federation of Korean Industries, he warned that high US tariffs could deal widespread blows to local industries and that South Korea needs to diversify its exports to markets including Europe and Southeast Asia, among other regions.