UPDATE 1-Shares of U.S. exporters fall as China retaliates on tariffs

(New throughout, updates prices after market open, adds comments, adds byline)

April 4 (Reuters) - Shares in U.S. exporters of everything from planes to tractors fell on Wednesday after China retaliated against the Trump administration's tariff plans by proposing duties on key U.S. imports including soybeans, planes, cars, beef and chemicals.

China was hitting back against U.S. President Donald Trump's plans to impose tariffs on $50 billion in Chinese goods with similar tariffs on U.S. goods even as Trump said the country is "not in a trade war with China."

Industrial stocks appeared to be the hardest hit. Shares in U.S. aerospace giant Boeing Co were last down 3.3 percent making it the biggest drag on the Dow though it was not immediately clear how much the tariffs would affect Boeing's newer products. The United States exported $15 billion of aircraft to China in 2016, ranking it equally with agricultural products like soybeans, according U.S. trade data.

Agricultural machinery maker Deere & Co was down 4.0 percent and DowDuPont Inc was down 1.3 percent.

"Everybody knew they were going to retaliate. The question was how strong of a retaliation. Today's move clearly shows that they mean business," said Adam Sarhan, chief executive of 50 Park Investments in New York.

Investors in the S&P 500's technology sector were also rattled since it has the biggest revenue exposure to China out of the benchmark's 11 major sectors. Chipmakers such as Nvidia Corp, with a 3.0 percent drop, and Intel Corp , with a 2.1 percent decline, were among the biggest percentage losers in that sector.

"These are some of the companies most exposed to potential tariffs. They would affect their business directly, immediately. said Brad McMillan, chief investment officer of Commonwealth Financial Network in Waltham, Massachusetts.

Shares of Caterpillar, also a big exporter to China, fell 2.4 percent. Chemical provider Chemours Co pared premarket losses but was still down 0.4 percent in the regular session.

Soybean exporter Archer Daniels Midland Co and another agribusiness Bunge Ltd reversed their premarket losses and were last up slightly.

With the three major U.S. indexes well off their January records after taking a massive tumble on Feb. 9, at least some investors were hoping that U.S. stocks will bounce back if earnings growth meets strong Wall Street forecasts in the first-quarter reporting season, which starts this month.

"Obviously we need kind of a quiet period on these headlines and we need to focus on what is ultimately important and that is earnings. So I am hopeful over the next couple of weeks that earnings will be that shiny object that everyone can focus on, said Jack Ablin, chief investment officer at Cresset Wealth in Chicago. (Additional reporting by April Joyner, Charles Mikolajczak and Lewis Krauskopf in New York, Taenaz Shakir in Bengaluru Editing by Jeffrey Benkoe and David Gregorio)