(CNN) The White House is defending President Donald Trump's threat to impose tariffs on at least $200 billion worth of Chinese goods, arguing the trade penalties are "necessary to defend this country."

"No one should be surprised," Peter Navarro, Trump's trade adviser, told reporters Tuesday on a White House conference call. "President Trump has given China every chance to change its aggressive behavior."

The United States has already announced a 25% tariff on $50 billion of Chinese goods, most of which will take effect as early as July 6, to punish China for stealing American trade secrets. China immediately promised to retaliate.

On Monday, Trump directed trade officials to identify an additional $200 billion worth of Chinese goods that will be subject to a 10% tariff if China doesn't back down. The President threatened to impose even more tariffs if China retaliates further.

On a day when the Dow dropped as much as 400 points because of fears of a US-China trade war, Navarro played down fears that escalating tariffs would harm the US economy. Instead, he insisted the dispute will have "relatively small effects."

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