NEW YORK (AP) _ American Express Co. in a move to bolster the management of its troubled Travel Related Services unit, named as president and chief operating officer a veteran executive of the company, Jonathan S. Linen.

The TRS unit has been hurt by falling profits due to the recession and problems with its Optima credit card.

Although it was once highly profitable and helped compensate for money- losing operations at American Express, TRS profit plunged 59 percent in 1991 to $396 million.

Linen, 48, started at American Express in 1969 as an assistant to then- chairman Howard Clark Sr. Linen spent a year as one of three presidents at TRS before he was named chief executive officer at the company's Shearson Lehman Brothers Inc. subsidiary.

Linen generally is credited with reviving Shearson, the nation's second- largest brokerage firm behind Merrill Lynch & Co. After losing $966 million in 1990, Shearson earned $207 million in 1991.

James Robinson III, chairman and chief executive officer of American Express, said Linen's main responsibility at TRS will be to build relationships with cardmembers and service establishments, reposition consumer lending and expand travel management businesses.

Last fall, Harvey Golub, chairman of IDS Financial Services, was named chairman and chief executive of TRS in a management shake-up that followed losses at the Optima credit-card business.

Under the new organizational structure, the TRS business units will report to Linen, who in turn will report to Golub.

Linen will be replaced at Shearson by John R. Laird, chairman and chief executive of Boston Co., American Express's money-management division.