Investing.com - Goldman Sachs (NYSE:GS) expects the S&P 500 to post a gain in 2018, despite the trade rift between the U.S. and China.In a note to clients, the Wall Street firm says trade tensions represent a "minimal risk" to the profits of S&P 500 companies.Goldman estimates that Chinese imports amount to just 3% of the U.S. GDP, while U.S. exports to China account for only 1% of the nation's overall goods and services.Goldman says the Trump administration's mention of $100 billion in additional tariffs is a "negotiating tactic."The firm reiterated its 2018 price target for the S&P 500 of 2,850. That's just about where the benchmark peaked in late January and would represent a 6% annual gain.