WASHINGTON (Reuters) - Mailed packages from China must undergo formal customs entry under new tariffs scheduled to be implemented on Tuesday, according to a notice from the U.S. Customs and Border Protection posted online on Monday.

Chinese imports that are eligible for temporary duty exemptions will also be subject to U.S. tariffs of 10%, the notice posted in the Federal Register said.

U.S. President Donald Trump on Monday delayed implementation of tariffs on Canada and Mexico until March 1, leaving only the Chinese packages affected for now.

CBP issued additional guidance for shippers on how to handle those shipments in light of the executive order on Chinese tariffs, and how to address with a manifest filed before the order takes effect.

"As we transition to execution of the Executive Order, it is extremely important that the trade maintain awareness of the shipments they are responsible for and are aware of the messaging that they are receiving from CBP," it said.

(Reporting by David Lawder and Andrea Shalal; writing by Susan Heavey; editing by Chris Reese and Lincoln Feast.)