Bank of America Merrill Lynch cut its rating on American Express shares to neutral from buy on Wednesday, saying it would "not be surprised" shareholders will sell the stock following recent out-performance.

"It's been a good run but ... given the broader market volatility and elevated uncertainty relating to the macro backdrop, we anticipate weaker sentiment," analyst Kenneth Bruce said in a note to investors.

"We think valuation will be restrained in a market backdrop highlighted by wild and unpredictable swings."

American Express shares fell 1.1 percent in premarket trading. The stock is positive on the year but has slid more than 10 percent this month.

The firm also cut its price target on American Express to $115 a share from $125 a share.