U.S. trade officials this week may impose new tariffs on solar panels from four Southeast Asian nations that American manufacturers have complained employ unfair subsidies that make U.S. products uncompetitive. The announcement, due on Tuesday, is the first of two preliminary decisions the Commerce Department will make this year in a trade case brought by Korea's Hanwha Qcells, Arizona-based First Solar and several smaller companies seeking to protect billions of dollars in investments in U.S. solar manufacturing. The domestic producers argue that competition from cheap imports by Chinese companies operating in Malaysia, Vietnam, Thailand and Cambodia threatens U.S. President Joe Biden's goal to boost domestic manufacturing of clean energy technologies needed to combat climate change.