American International Group Inc's shares fell 5.4 percent on Tuesday after speculation that the insurer was planning to sell shares, two portfolio managers said.

The source of the speculation was not clear, although earlier on Tuesday, an article by CNBC television host Jim Cramer published on argued that AIG ought to sell shares.

AIG declined to comment.

The two portfolio managers who had heard the rumors declined to comment because they are not authorized to speak to the media.

AIG's shares closed down 5.37 percent at $45.80.

(Reporting by Dan Wilchins)