U.S. President Donald Trump’s tariff letters that threaten steep duties on several countries, including key allies, have led to “shock” and “regret” even as nations expressed optimism that negotiations would yield favorable results.

Japanese Prime Minister Shigeru Ishiba said the latest tariff announcement was “truly regrettable,” while stressing that he would continue negotiations with the U.S. government, according to local media reports.

Japan is among the two nations set to to see an increase in the “reciprocal” tariff rate that Trump had announced in April. Japanese imports into the U.S. will face a 25% levy, starting Aug. 1, according to the White House, higher than the 24% announced earlier.

At a meeting with cabinet ministers on Japan’s strategy on tariffs, Ishiba noted that the Trump administration had proposed a plan to continue talks until the August deadline.

“Depending on Japan’s response, the content of the letter could be revised,” Ishiba said at the meeting Tuesday morning, hours after Trump posted a copy of his tariff letters on social media platform Truth Social.

Meanwhile, South Korean leaders vowed to accelerate tariff negotiations with the Trump administration to “swiftly resolve trade uncertainties,” Yonhap News reported, citing a statement from the Ministry of Trade, Industry and Energy.

Trump announced a 20% blanket tariff on imports from the country, unchanged from his “reciprocal” tariff level announced in April.

Yeo Han-Koo, South Korea’s trade minister, also reportedly asked U.S. to lower tariffs on automobiles, steel and other goods for Korean companies in a meeting with U.S. Commerce Secretary Howard Lutnick in Washington.

Thai Finance Minister Pichai Chunhavajira said Tuesday that he was “a little shocked” by the latest tariff rate but remained “confident” that it will drop to levels similar to those on other countries, according to Reuters.

Thailand faces a 36% tariff on its exports to the U.S. — one of the steepest rates among the 14 nations Trump mentioned Monday — unchanged from the April level.

Malaysia, which saw its tariff rate rise to 25% from the previously threatened 24%, said it will continue to engage with the U.S. to address outstanding issues.

“Malaysia is committed to continuing engagement with the US towards a balanced, mutually beneficial, and comprehensive trade agreement,” the Ministry of Investment, Trade and Industry said in a statement Tuesday.

Outside Asia, South African president Cyril Ramaphosa disagreed with the 30% tariff rate in a statement posted on X. The levy was “not an accurate representation of available trade data,” Ramaphosa said, adding that 77% of U.S. goods entered the country with zero tariff.

South Africa will continue with its diplomatic efforts toward a “more balanced and mutually beneficial trade relationship with the United States,” he said.

Deborah Elms, head of trade policy at a think tank Hinrich Foundation, said countries’ negotiating efforts with Trump seemed to have little impact on the outcome.

“ASEAN members that worked hard to develop packages received almost all the same treatment as countries that either did not fly to DC or were not invited to meet,” Elms said, adding that Trump may still be targeting Asian nations out of “worries over regional supply chains that include content from China.”

Trump shared screenshots of letters detailing new tariff rates for over a dozen countries in a series of social media posts Monday, allowing room for further negotiations before the renewed deadline of Aug. 1. The letters indicated that the U.S. could consider adjusting the new tariff levels.