China could face difficulties fulfilling its commitment in the so-called phase one trade deal with the U.S., allowing U.S. President Trump to once again raise tariffs on Chinese goods, a trade expert warned.

That's especially the case when the deal - expected to be signed in Washington on Wednesday - would involve Beijing increasing its imports of U.S. goods and services by at least $200 billion over two years, said Deborah Elms, executive director at consultancy Asian Trade Centre.

To meet that additional $200 billion, China would have to buy a "crazy amount" of U.S. "agricultural goods, machinery especially aircraft and energy products," noted Elms. For some products, Beijing may have to more than double its purchases by reducing tariffs on those imports and stop buying them from other sources.

"If the Chinese don't achieve those purchase price targets, the U.S. could impose new tariffs or remove existing promises or all sort of things could happen. I think the risks remain for companies between now and at least November that phase one doesn't even hold," Elms told CNBC.

The U.S., especially the agriculture sector, could also find it challenging to supply that amount of products to China, said Elms.