China has agreed to allow imports of rice from the US for the first time.
The agreement gives US farmers access to the world's biggest rice consumer, with China importing about 5 million tonnes last year.
It follows trade talks between the two countries that resulted in little progress on other issues.
While China opened its rice market in 2001, a lack of protocols on pests and plant diseases effectively stopped imports taking place.
The organisation representing the US rice industry said the new agreement was the most complex of its kind, and set strict standards for US exporters to protect against the introduction of certain pests to China.
USA Rice added it would work with the US Department of Agriculture (USDA) to make sure the industry complied with the rules.
"We know China wants to send a team here to inspect mills and facilities certified to ship to China, and we are working with USDA to make that happen in the quickest and most efficient way," said Carl Brothers, chairman of the USA Rice International Trade Policy Committee.
US authorities and the industry have both hailed the agreement as a huge win.
"This market represents an exceptional opportunity today, with enormous potential for growth in the future," said US Agriculture Secretary Sonny Perdue.
According to OECD projections, the average person in China will consume 75kg of rice a year by 2024, compared with an average of 13kg in North America and 5kg in Europe.
USA Rice said China consumes the equivalent of the entire US annual output every two weeks.
Agriculture appears to be a bright spot in an otherwise thorny trade relationship between the two countries.
The announcement follows a round of contentious trade talks in Washington that appeared to end with little progress on tricky issues like China's steel exports or its $347bn (£268bn) trade surplus with the US.
The two sides didn't issue any joint statement following the talks, and cancelled scheduled press conferences.
The US has indicated that it might impose tariffs or quotas on Chinese steel, but since the talks wrapped up China has suggested that there was some progress on the issue.
Beijing's embassy in Washington said the two sides "had in-depth discussion on cutting excess steel production capacity in the world and agreed to active and effective measures to jointly address this global issue".