DETROIT (Reuters) - Shares of General Motors Co (>> General Motors Company) and Ford Motor Co (>> Ford Motor Company) fell more than 5 percent early on Wednesday after Morgan Stanley said the U.S. automakers are exposed to risks of a cyclical downturn in major markets.

In separate research notes, Morgan Stanley analyst Adam Jonas said GM and Ford had not accounted for what he expected to be the impact of lower prices for their vehicles in North America, where both companies have made the lion's share of their profits in recent years. Morgan Stanley said Ford and GM also face cyclical downturns in China and Europe.

As a result, Jonas said GM might have to sell 14 million vehicles in the United States to break even, while Ford's breakeven point could be as high as 14.6 million vehicles.

GM has said its breakeven point is between 10 million and 11 million vehicles and Ford has said it can profit at 11 million vehicles in U.S. sales.

Shares of GM fell as much as 5.3 percent and were last down 3.1 percent at $28.48 on the New York Stock Exchange. Ford shares were down as much as 6.6 percent before rebounding to trade 3.7 percent lower at $11.96 on the NYSE.

Shares of Fiat Chrysler Automobiles (>> Fiat Chrysler Automobiles NV) fell as much as 5.9 percent and closed down 4 percent at 5.52 euros in Milan. Fiat Chrysler shares were down 2.5 percent at $6.15 on the NYSE.

Morgan Stanley, which sidelined coverage of GM and Fiat Chrysler for several months as it advised GM amid merger overtures from Fiat Chrysler, reinstated coverage of GM with an "underweight" rating and price target of $26 a share.

It reinstated coverage of Fiat Chrysler with an "overweight" rating and price of 10 euros per share, noting that the company is willing to "explore asset sales" or other sales to "ring-fence the value of (Fiat Chrysler's) most desirable businesses."

Morgan Stanley kept its "underweight" rating on Ford but lowered its price target to $12 a share from $15.

(Reporting by Bernie Woodall; Editing by Paul Simao)