LONDON - U.S. President Donald Trump said a trade agreement with China might have to wait until after the U.S. presidential election in November 2020, denting hopes of a quick resolution to a dispute that has weighed on the world economy.

"I have no deadline, no. In some ways, I think I think it's better to wait until after the election with China," Trump told reporters in London, where he was due to attend a meeting of NATO leaders.

"In some ways, I like the idea of waiting until after the election for the China deal. But they want to make a deal now, and we'll see whether or not the deal's going to be right; it's got to be right."

European share prices, U.S. stock futures and the Chinese yuan currency fell on Trump's comments.

Investors have been hoping that the United States and China can avert an escalation of their trade tensions. U.S. officials have previously said a deal could happen this year, depending on China.

The pan-European STOXX 600 index turned negative as Trump spoke, weighed down by export-heavy mining stocks.

Washington and Beijing have yet to ink a so-called "phase one" agreement announced in October, which had raised hopes of a de-escalation.

Trump and Chinese President Xi Jinping had planned to meet and sign the preliminary trade deal at an Asia-Pacific leaders' summit in Chile in mid-November, but the summit was canceled.

Trump, who had said in September that he did not need a deal before the 2020 election, sought on Tuesday to put pressure on Beijing.

"The China trade deal is dependent on one thing - do I want to make it, because we are doing very well with China right now, and we can do even better with a flick of a pen," he said. "And China is paying for it, and China is having by far the worst year that they have had in 57 years. So we'll see what happens."

China reported its slowest economic growth in 27 years in October as the trade tensions with the United States hit its manufacturing sector.

On Monday, before travelling to London, Trump said U.S. legislation backing protesters in Hong Kong was not making trade negotiations with China easier, but he believed Beijing still wanted a deal with the United States.

U.S. Commerce Secretary Wilbur Ross has said that Dec. 15, when a further 15% U.S. tariff on about $156 billion worth of Chinese imports is set to take effect, is a natural deadline for an agreement.