(Bloomberg) -- Stock traders who dodged one tariff bullet Monday are starting to resign themselves to a volatile week as a second wave of trade belligerence burst forth from Donald Trump’s administration.

Signs of hardening lines from the U.S. and China have Wall Street bracing for a resumption of the tit-for-tat posturing that marked trade skirmishes past. While U.S. equity markets were largely spared the pummeling that landed on Asia Monday after Trump warned he would raise tariffs, major indexes took a fresh hit Monday night.

Futures on the S&P 500 slipped as much as 0.7 percent after the president’s top trade negotiator, Robert Lighthizer, said the U.S. plans to raise tariffs on Chinese goods on Friday, accusing Beijing of backpedaling on commitments it made during negotiations.

“If they are in fact raised, it would weigh heavily on markets,” said Peter Jankovskis, co-chief investment officer at Oakbrook Investments, adding that the talk still sounds to him like negotiating tactics. “What they’re saying is they’re going to make an announcement of tariffs on that date. But I don’t believe they can actually go through and implement it.”

The lurch in futures, which was pared to about 0.5 percent at 6:13 p.m. in New York, followed a roller-coaster session in which a decline that reached 1.6 percent in the S&P 500 cash index narrowed to 0.5 percent by the close.

“The market took the relatively optimistic view today that the president’s tweets were a negotiation tactic and maybe he wasn’t absolutely serious,” said Michael O’Rourke, JonesTrading’s chief market strategist. “Now you have the confirmation that he’s serious and that trade talks are deteriorating fast. We’re up 17 percent this year largely because of the expectation of a trade deal, I expect the markets to have a hard time with this.”

The U.S. and China had been making substantial progress on a trade deal, but in the past week China has reneged on some of its promises, Lighthizer said. Significant issues remain unresolved, including whether tariffs will remain in place, he said.

Judging by previous bouts of trade aggression by Trump, it would’ve been wishful thinking to believe this episode would be limited to one day. Since taking aim at China about 14 months ago on Twitter, most of his public campaigns have lasted for multiple days. On the other hand, while the president’s musings often immediately spooked the market, equities usually finished up by the end of the day. In virtually every instance, shares were higher a week later.

“I still think the market is looking for some type of resolution and hoping and praying that that will happen,” said Nathan Thooft, Manulife Asset Management’s head of global asset allocation. “There’s no doubt if they go into effect, if they stay in effect, the markets aren’t going to like that.”

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