President Donald Trump said on Wednesday that he would impose a 10% baseline tariff on all imports to the U.S. and higher duties on dozens of other countries, including some of the United States' biggest trading partners, deepening a trade war that he kicked off on his return to the White House.

The sweeping duties would erect new barriers around the world's largest consumer economy, reversing decades of trade liberalization that have shaped the global order. Trading partners are expected to respond with countermeasures of their own that could lead to dramatically higher prices for everything from bicycles to wine.

U.S. stock futures sank after the announcement, following weeks of volatile trading as investors speculated about how the incoming tariffs might affect the global economy, inflation and corporate earnings. U.S. stocks have erased nearly $5 trillion of value since February.

"It's our declaration of independence," Trump said at an event in the White House Rose Garden.

Chinese imports will be hit with a 34% tariff, according to Trump, on top of the 20% levy that he previously imposed on that country. Close U.S. allies were not spared, including the European Union, which faces a 20% tariff.

A White House official, speaking on condition of anonymity, said the higher penalties will take effect on April 9 and will apply to about 60 countries in all. The baseline 10% tariff will take effect on Saturday, the official said.

The "reciprocal" tariffs, Trump said, were a response to duties and other non-tariff barriers put on U.S. goods.

"In many cases, the friend is worse than the foe in terms of trade," Trump said.

Canada and Mexico, the two largest U.S. trading partners, already face 25% tariffs on many goods and will not face additional levies from Wednesday's announcement.

The reciprocal tariffs do not apply to certain goods, including copper, pharmaceuticals, semiconductors, lumber, gold, energy and "certain minerals that are not available in the United States," according to a White House fact sheet.

Following his remarks, Trump signed an order to close a trade loophole used to ship low-value packages - those valued at $800 or less - duty-free from China, known as "de minimis." The order covers goods from China and Hong Kong and will take effect on May 2, according to the White House.

Chinese chemical makers are the top suppliers of raw materials purchased by Mexico's cartels to produce the deadly drug, U.S. anti-narcotics officials say. A Reuters investigation last year showed how traffickers often route these chemicals through the United States by exploiting the de minimis rule. China has repeatedly denied culpability.

Trump is also planning other tariffs targeting semiconductors, pharmaceuticals, and potentially critical minerals, the official said.

Trump's barrage of penalties has rattled financial markets and businesses that have relied on trading arrangements that have been in place since the middle of last century.

Earlier in the day, the administration said a separate set of tariffs on auto imports that Trump announced last week will take effect starting on Thursday.

Trump has already imposed 20% duties on all imports from China and 25% duties on steel and aluminum and extended them to nearly $150 billion worth of downstream products.

His advisers say the tariffs will return strategically vital manufacturing capabilities to the United States.

Outside economists have warned that tariffs could slow the global economy, raise the risk of recession, and increase living costs for the average U.S. family by thousands of dollars. Businesses have complained that Trump's barrage of threats has made it difficult to plan their operations.

Tariff concerns have already slowed manufacturing activity across the globe, while also spurring sales of autos and other imported products as consumers rush to make purchases before prices rise.

(Reuters - Additional reporting by Kanishka Singh and Steve Holland; Writing by Andy Sullivan; Editing by Diane Craft and Alistair Bell)