NEW YORK (Reuters) - A forward-looking measure of U.S. non-residential construction activity weakened last month but remains above a record low reached in March, an architects' trade group said on Wednesday.

The Architecture Billings Index fell more than two points from the month before to a reading of 43.4 in May, according to the American Institute of Architects. Any reading below 50 indicates a decline in billings, a leading indicator of construction activity about nine to 12 months in the future.

The ABI reached a record low of 39.7 in March.

"We've seen a dramatic contraction in design activity in recent months," said AIA Chief Economist Kermit Baker.

Activity is weakest in the Western United States, the AIA said. Among construction sectors it tracks, only the institutional sector is in expansion, reflecting demand for government buildings, schools and hospitals.

Companies that sell into the non-residential construction market include diversified manufacturer Honeywell International Inc , Cooper Industries Ltd , a maker of electrical products and tools, lighting maker Acuity Brands Inc , electrical components maker Thomas & Betts Corp , and Johnson Controls Inc , which provides heating, ventilation and cooling systems.

(Reporting by Nick Zieminski; Editing by Braden Reddall)