UPDATE 3-Shell says may sell or shut Canadian refinery

* Plans decision on refinery's fate in coming months

* Refining margins expected to stay weak

* Montreal East facility employs about 500 people (Adds comments by union leader)

By Jeffrey Jones and Tom Bergin

CALGARY/LONDON, July 9 (Reuters) - Royal Dutch Shell Plc (RDSa.L) said on Thursday it is conducting a strategic review of its Montreal East refinery, which may lead to a closure or sale as the industry struggles with weak profit margins.

The Anglo-Dutch oil major will decide in the coming months the future of the 130,000 barrel per day crude processing facility, which could also result in its continued operation by Shell or conversion into a terminal, a spokesman said.

Shell has been reviewing its refinery portfolio in recent years, scaling back in areas such as Europe, where it believes there will be little or no growth in demand.

The Montreal East facility, one of three refineries in Quebec, employs about 500 people. It opened in 1933.

The head of the union local at the refinery said Shell informed the employees about its review on Tuesday, but gave no reason for the move.