Talks between the U.S. and China to resolve their yearlong trade standoff appeared to be on life support Monday, with Beijing struggling to respond to a pair of tweets by President Donald Trump that threaten an escalation of tariffs by the end of the week.

China's foreign ministry said that officials were still planning to travel to the U.S. for the next round of talks — but was unable to confirm when amid signs that a delay is now being considered. Meanwhile, a media blackout on Trump's threat left investors baffled as stocks and the yuan tumbled on rumors that the trade war is now back on.

"We are now trying to get more information on the relevant situation," ministry spokesman Geng Shuang told a briefing in Beijing. "What I can tell you is that the Chinese team is preparing to travel to the U.S. for trade talks."