US President Donald Trump on Tuesday warned China against waiting out his first term to finalize any trade deal, saying if he wins re-election in the November 2020 US presidential contest, the outcome could be no agreement or a worse one. “The problem with them waiting ... is that if & when I win, the deal that they get will be much tougher than what we are negotiating now...or no deal at all,” Trump said in a post on Twitter, as the latest U.S-China trade talks began in Shanghai. Trump said China appeared to be backing off on a pledge to buy US agricultural products, which US officials have said could be a goodwill gesture and part of any final pact. “China ... was supposed to start buying our agricultural product now — no signs that they are doing so. That is the problem with China, they just don’t come through,” Trump wrote in a series of tweets. US and Chinese officials restarted negotiations after talks stalled in May, in a bid to end the year-long trade war marked by tit-for-tat tariffs, but must still resolve deep differences, keeping expectations for this week’s two-day meeting low. The trade war between the world’s two largest economies has rattled global financial markets that have also been pressured by this week’s US Federal Reserve policy meeting and renewed concerns over Britain’s exit from the European Union. Speaking to reporters at the White House, Trump said the trade talks were going well with China, but added the United States would “either make a great deal or no deal at all.” “We’ll see what happens,” he told reporters. The US negotiating team arrived for talks in Shanghai Tuesday afternoon but there was no sighting of US Trade Representative Robert Lighthizer or US Treasury Secretary Steven Mnuchin. The US and Chinese delegations later appeared to have reached Shanghai’s historic Fairmont Peace Hotel where sources say the US delegations are having dinner, but both teams avoided the media and did not make public comments. Trump has targeted China as part of his “America First” campaign that helped him win the White House in 2016 and has staked his re-election bid in part on the strength of the US economy. He has sought to negotiate various trade deals with China as well as Europe and other countries as part of his efforts to make good on his campaign promises. On Tuesday, Trump also reiterated that Beijing might stall talks in hopes of inking a laxer deal with “somebody like Elizabeth Warren or Sleepy Joe Biden,” singling out two Democratic presidential frontrunners, before reversing course. “China is dying to make a deal with me. But whether or not I do it, is up to me. It’s no up to them.” he said. “China is willing to give up a lot. But that doesn’t mean I’m willing to accept it.”