New York (CNN Business) It turns out trade wars are not short and not so easy to win, as President Donald Trump once tweeted. As the US-China trade war drags on, economists are sharpening their pencils, forecasting what a protracted trade war would cost.

The Organization for Economic Cooperation and Development warns an escalation would hurt the US economy and damage the rest of the world, shaving 0.7% from global growth by the year 2021. That's roughly $600 billion. The OECD sees the potential for new trade barriers between the United States and the European Union and Brexit-related uncertainties, as well.

In an analyst note, Morgan Stanley finds the window for resolving the trade dispute is narrowing. Without resolution in the next month, the trade war will bite into global growth

"If talks stall, no deal is agreed upon and the US imposes 25% tariffs on the remaining $300 billion of imports from China, we see the global economy heading towards recession," Morgan Stanley's analysts wrote. Under that scenario, the US Federal Reserve would have to cut interest rates, ultimately back to zero and China would need huge new stimulus, they said.

At Bank of America, analysts report the trade war has already hurt confidence on Main Street, noting a protracted trade war "could have a meaningful impact on consumer spending."

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