President Trump said on Monday that his administration was planning to provide about $15 billion in aid to help U.S. farmers whose products may be targeted with tariffs by China amid a deepening trade war.

He did not provide any more details on what kind of an aid package it would be, Reuters reports.

American farmers, a key constituency of Trump, have been among the hardest hit in the trade war. Soybeans are the most valuable U.S. farm export, and shipments to China dropped to a 16-year low in 2018, while soybean futures prices last week fell this week to 11-year lows.

U.S. Agriculture Secretary Sonny Perdue said on Friday that Trump had asked him to create a plan to help American farmers cope with the heavy impact of the U.S.-China trade war on agriculture.

A new aid program would be the second round of assistance for farmers, after the Department of Agriculture's $12 billion plan last year to compensate for lower prices for farm goods and lost sales stemming from trade disputes with China and other nations.

"Out of the billions of dollars that we're taking (in in tariffs on Chinese imports), a small portion of that will be going to our farmers, because China will be retaliating, probably to a certain extent, against our farmers," Trump said.

On Monday, China said it would impose higher tariffs on a range of U.S. goods, including frozen vegetables and liquefied natural gas, striking back in its trade war with Washington after Trump warned it not to.

Last year Beijing imposed tariffs on imports of U.S. agricultural goods, including soybeans, grain sorghum and pork as retribution for U.S. levies. Soybean exports to China have plummeted over 90 percent and sales of U.S. soybeans elsewhere failed to make up for the loss.