WASHINGTON—The Trump administration said Tuesday it would extend $12 billion in emergency aid to farmers amid signs the U.S. agricultural sector is beginning to feel the impact of President Donald Trump’s escalating trade disputes with major U.S. trading partners.

Agriculture Secretary Sonny Perdue said the U.S. government would provide incremental payments to support prices of some of the hardest-hit commodities, including soybeans, sorghum, cotton, corn, wheat and pork.

“This is a short-term solution that will give President Trump and his administration time to work on long-term trade deals,” Mr. Perdue told reporters. Agriculture Department officials said the aid wouldn’t need congressional approval.

Mr. Perdue said the move, tentatively planned for the coming months, was in response to what he called U.S. trading partners’ “illegal retaliation” to the policies of Mr. Trump, who has ordered tariffs on imports ranging from metals to materials to clothing to electronic parts. Those tariffs apply to goods from a broad range of countries, including China and those of the European Union.

U.S. trading partners are retaliating, with ominous implications for the American Farm Belt. China, a huge market for U.S. agricultural exports, has applied tariffs on $34 billion worth of U.S. goods, including soybeans and pork. Other places applying retaliatory tariffs include allies such as Canada, Mexico and the EU.