WASHINGTON — U.S. President Donald Trump signed a proclamation Thursday to impose new tariffs on drones and their components, including a 15 percent levy on imports from Korea, Japan and other economies, the White House said, portraying the move as an effort to bolster national security. Under the proclamation, a 100 percent tariff will be imposed on certain drones, including larger ones and those with thermal imaging capabilities, which are sensitive for national security purposes, while a 25 percent tariff will apply to certain smaller drones that raise security concerns. Imports from Korea, Japan, the European Union, Liechtenstein, Switzerland and Taiwan will face a 15 percent tariff, while a 10 percent duty will apply to those from Britain. The new tariffs are set to take effect at 12:01 a.m. on Sept. 3 this year, except for those on less-sensitive drone components that will take effect at 12:01 a.m. on Feb. 9 next year, according to the proclamation. Trump announced the tariffs under Section 232 of the Trade Expansion Act of 1962 — a law that allows the president to adjust impor