Trump will explain tariffs on electronics on Monday

Republican Sen. Thom Tillis, who grilled the president's top trade negotiator on Capitol Hill on Tuesday, expressed deep frustration with the tariffs as he entered the Senate Finance Committee.

"Of course, it concerns me. I mean my god, it's a stability issue. Businesses hate uncertainty. We've got a lot of uncertainty," he told ABC News.

When the hearing got underway, Tillis drove home that point.

"Whose throat do I get to choke if this proves to be wrong?" Tillis said.

Other Republicans are standing by the president but admit they don't know what the president's next move is.

Sen. John Kennedy, R-La., told ABC News the president is "absolutely correct" that foreign countries have trade barriers, but he also acknowledged he doesn't know what the president's "game plan" is.

"Whether this will have a happy ending or a sad ending depends in large part what President Trump does next," Kennedy said.

-ABC News' Rachel Scott and Allison Pecorin

White House press secretary Karoline Leavitt confirmed on Tuesday that Trump's threatened additional 50% tariff on China will go into effect early Wednesday, bringing the total tariff rate against Beijing to 104%.

"They will be going into effect at 12:01 a.m.," she said.

"It was a mistake for China to retaliate. The president, when America is punched, he punches back harder," Leavitt said. She added Trump believes China "wants to make a deal" but doesn't know where to start.

White House press secretary Karoline Leavitt was asked during Tuesday's briefing if President Trump is operating on any specific timeline for when he wants to complete negotiations on tariffs.

"Well, we always move at Trump speed here at the White House, which is incredibly fast," she responded.

Leavitt added, "the president likes to get things done, but he's very much focused on ensuring that these deals are good for the American worker, they are good for American manufacturing, and again, that they tackle these crippling deficits with these countries."

They will be "tailor-made deals," Leavitt said, with Trump directing his entire trade team to be involved in the effort.

Stocks in Europe and Asia partially rebounded Tuesday, buoyed by signals from the White House that it is open to talks on tariffs with countries.

The UK’s FTSE, Germany’s DAX and the pan-European Stoxx 600 closed at 2.5% or above.

In Asia, Japan’s Nikkei jumped over 6%, while China’s Shanghai Composite index closed at 1.4%.

However, analysts warn further volatility is likely, with Trump’s higher-rate tariffs due to go into effect Wednesday and the EU also preparing to impose its own retaliatory tariffs.

The EU reportedly plans to impose import duties of up to 25% on a range of US goods, including diamonds, motorbikes, luxury boats, domestic appliances, tobacco, poultry and many other agricultural products.

-ABC News' Patrick Reevell