China is not purchasing U.S. crops as the world's two largest economies scramble to end their trade war, President Donald Trump said Thursday.

The president tweeted that Beijing "is letting us down" by not buying American agricultural products "that they said they would." The development could bode poorly for efforts to reach a trade agreement, as U.S. officials have said they expect China to purchase crops as part of ongoing talks.

"Hopefully they will start soon!" Trump said.

Trump tweet: Mexico is doing great at the Border, but China is letting us down in that they have not been buying the agricultural products from our great Farmers that they said they would. Hopefully they will start soon!

Washington and Beijing have reengaged in trade talks in recent weeks after discussions collapsed in May. At the time a developing deal fell apart, Trump accused China of backing out of major commitments.