(CNN) President Donald Trump complained on Thursday that China hasn't yet begun purchasing US agricultural products -- a sign that some of the commitments he believed were made with Chinese President Xi Jinping last month weren't as solid as advertised.

"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!" Trump wrote on Twitter.

The tweet is reflective of what people familiar with the talks say were loose agreements Trump secured during his 90-minute meeting last month with Xi. But according to people familiar with the talks, the Chinese side has said they made no firm commitments to purchase US agricultural products, despite Trump's claims otherwise after the meeting.

"China is going to be buying a tremendous amount of food and agricultural product, and they're going to start that very soon, almost immediately. We're going to give them lists of things that we'd like them to buy," Trump said at the time.

In exchange, Trump agreed to forestall new tariffs on Chinese products and ease some restrictions on Huawei, the Chinese telecom giant. Without the new agricultural purchases, it's not clear what Trump is getting in return for those moves.

Read More