The US president declared the country's "economic independence" at a grand event in the White House Rose Garden before announcing a new round of tariffs.

President Donald Trump said Wednesday he will impose a base tariff of 10 percent on all U.S. imports and higher tariffs on some of the country's major trading partners, escalating a trade war that began upon his return to the White House.

The sweeping tariffs 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 result in dramatically higher prices for everything from bicycles to wine.

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

Trump displayed a sign listing reciprocal tariffs, including 34% for China and 20% for the European Union, in response to duties imposed on US products.

Other details were not immediately apparent as Trump continued to make comments that echoed his longstanding complaints that American workers and businesses are being hurt by global trade.

Uncertainty has shaken financial markets and businesses that have relied on trade agreements in place since 1947.

The administration has said the new tariffs will take effect immediately after Trump announces them, although it has not yet published the official notice required for their implementation.

However, the administration has issued an official notice that a separate set of tariffs on auto imports that Trump announced last week will take effect starting April 3.

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