The top White House trade official says the United States is defending itself from China's economic aggression after President Trump threatened China with new tariffs on $200 billion worth of imports.Trump announced Monday that he has asked the U.S. Trade Representative to identify more Chinese imports for additional tariffs of 10 percent. Trump said if China refuses to change its practices and moves on its threatened tariffs against the U.S., his administration will move ahead with the additional tariffs.Peter Navarro, Director of White House National Trade Council, told reporters in a conference call on Tuesday the White House has given China every opportunity to change its "aggressive behavior." He said a 2017 Mar-a-Lago summit and several rounds of trade talks between high-level officials in the past year have not yielded any progress."It is important to note here that the actions President Trump has taken are purely defensive in nature," he said. "They are designed to defend the crown jewels of American technology from China's aggressive behavior."Navarro said China is seeking to acquire American technology six ways, including physical theft and cyber theft, forced technology transfer, evasion of export controls, export restraints on raw materials, information harvesting campaigns designed to exploit the openness of the U.S. economy, and acquisition of the "crown jewels" of American technology by China's state-backed funds.In a statement issued Tuesday, China's commerce ministry criticized Trump's latest move as nothing more than "extreme pressure and blackmail" that "deviates from the consensus reached by both sides" during multiple talks.Stocks tumble U.S. stock market tumbled on Tuesday following the latest salvos between Washington and Beijing. The Dow Jones Industrial Average lost more than 1.1 percent at the close of trading and other major indexes posted losses as well.However, Navarro dismissed concerns about how the administration's trade policy would affect the financial markets and global economy, saying it will have only a "relatively small effect." He argued the actions are necessary to defend America and that the steps will ultimately benefit the country and global trading system.The White House officially announced on June 15 it will impose additional 25 percent tariffs on $50 billion worth of Chinese goods, and will start collecting the additional duties on $34 billion worth of imports on July 6. An additional $16 billion worth of products are undergoing further review. China immediately retaliated, saying it will impose tariff measures of the same scale and intensity. Beijing announced it will impose an additional 25 percent tariff on a total of 659 U.S. imports worth about $50 billion. The products targeted included automobiles and agricultural products, such as soybeans, corn, and wheat, which will also start on July 6.Navarro said the administration is working on measures to help U.S. farmers caught in the middle of the tit-for-tat trade dispute, but did not reveal details of such measures.He did not reveal plans for further trade talks between Washington and Beijing, but added "our phone lines are open, they have always been open."