The Trump administration signaled on Tuesday that it was ready to negotiate deals with countries targeted by sweeping tariffs, saying that 70 governments had approached the United States to try to roll the levies back and that officials would begin talks with Japan, South Korea and other nations.

But President Trump and his advisers have been clear that these entreaties will not stop the next round of tariffs from going into effect just after midnight Wednesday, including another 50 percent duty on China. As a result, tariffs on Chinese goods will be at least 104 percent.

On Tuesday, Mr. Trump acknowledged his tariffs had been “somewhat explosive,” but he defended the policy and said “the money is pouring in at a level we’ve never seen before.”

“We have a lot of countries coming in to make deals,” he said Tuesday afternoon at a White House event.

Earlier in the day, Mr. Trump said on social media that he had “a great call” with South Korea’s acting president, Han Duck-soo, about trade and tariffs, and that South Korean officials were heading to the United States for talks. He also expressed optimism that a trade war with China could be averted.

“China also wants to make a deal, badly, but they don’t know how to get it started,” Mr. Trump wrote. “We are waiting for their call. It will happen!”