WASHINGTON — A deal seemed so close.

As recently as May, the Trump administration and China seemed on the verge of resolving their dispute over Beijing’s combative trade policies.

Then it all collapsed. A cease-fire, declared by Presidents Donald Trump and Xi Jinping in June, failed to stick.

Now, global financial markets are shaking and central banks across the world are trying to cushion their economies from the worst by slashing interest rates — all in the expectation that a trade war between the world’s two biggest economies will continue to rage, probably through the 2020 U.S. presidential election.

“The U.S.-China trade talks are in serious trouble,” said Wendy Cutler, a former U.S. trade negotiator who is now vice president at the Asia Society Policy Institute. “There is less and less trust on both sides, coupled with a growing sense in both Washington and Beijing that they may be better off without a deal, at least for the time being.”

The past week has been especially rocky. A week ago, Trump abruptly announced that starting Sept. 1, he would impose tariffs on the remaining $300 billion in Chinese imports that he’s so far spared. On Monday, Beijing struck back: It halted purchases of U.S. farm products — a blow to a critical Trump political base in the Midwest — and let its currency sink to its lowest level in 11 years. A lower-valued Chinese currency, the yuan, gives its exporters a competitive edge over foreign rivals.

Beijing’s currency move led the U.S. Treasury Department to declare China a currency manipulator for the first time since 1994. That step could eventually pave the way for additional sanctions. But for now, it stands mainly as a symbol of the increasingly rancorous feud between Washington and Beijing.

“Both sides are retrenching,” said Timothy Keeler, a former chief of staff at the Office of the U.S. Trade Representative and now a partner at the law firm Mayer Brown.”

The prospect that the U.S.-China trade war will go on indefinitely poses a serious threat to a global economy that was already weakening. The International Monetary Fund expects world trade to slow in 2019 for a second straight year.

The Trump administration says the Chinese are cheating in their drive to dominate such cutting-edge technologies as artificial intelligence and quantum computing.

Reaching a substantive deal was bound to be difficult, not least because it would require China to scale back its economic aspirations — aspirations that have become central to its self-identity. Yet at the start of May the two sides seemed to be moving toward some kind of meaningful agreement.

Abruptly, Trump accused Beijing on May 5 of reneging on commitments it had made earlier and said he would raise tariffs on $200 billion in Chinese products, a threat he made good on five days later. The U.S. also began readying tariffs on an additional $300 billion in Chinese goods.

Trump and Xi offered a respite in June. Trump agreed to delay the new tariffs while talks resumed. After a 12th round of negotiations in Shanghai last month made scant progress, Trump busted the truce and said he’ll tax the $300 billion on Sept. 1. He accused Beijing of trying to slow-walk the talks until 2020 in the hope that he would lose the election and they could negotiate with a Democratic president instead.