SINGAPORE - Hong Kong stocks are cheap but may miss out on the benefits of China's economic support, analysts at Goldman Sachs said, while Morgan Stanley warned tensions and tariffs could hurt, as both brokerages downgraded market forecasts.

Goldman Sachs trimmed its recommendation on Hong Kong shares to "underweight" from "market weight".

Morgan Stanley downgraded China to slight "underweight" from "equal weight" in emerging markets, with analysts noting that efforts to revive the economy and a Republican sweep of Congress and the White House could significantly impact markets.

"We expect even stronger headwinds on corporate earnings and market valuation in the coming months," Morgan Stanley analysts said in a note dated Nov. 17.

Morgan Stanley's base-case target for China's CSI300 is 4,200 by end-2025, about 4.7% above the 4,011 level traded earlier in the day. It projects the Hang Seng at 19,400, slightly below Monday's 19,655.

Goldman Sachs is more bullish on mainland stocks, setting a 2025 target on the CSI300 at 4,600, but expects weakness in Hong Kong companies on the MSCI Hong Kong index.

"Although valuations are not demanding, Hong Kong does not offer much economic or earnings growth," Goldman analysts said in an Asia-Pacific portfolio strategy note published on Sunday.

"The property and retail sectors remain under pressure and the economy may not benefit as much from policy support in China as it previously has, given China's focus on bolstering the domestic economy."

Both U.S. banks expect the yuan to weaken, with Goldman forecasting a dollar/yuan exchange rate of 7.5 at the end of next year and Morgan Stanley 7.6. The yuan traded at 7.2371 per dollar on Monday.

Both brokerages recommend investing in mainland shares over Hong Kong-listed ones, as the mainland market is less sensitive to global sentiment or currency fluctuations.

(Reporting by Tom Westbrook; Editing by Christian Schmollinger and Sherry Jacob-Phillips)