PORTLAND – Operators of Amtrak’s Downeaster and the owner of 77 miles of track have reached an impasse on the issue of speed, sending the matter back to the U.S. Surface Transportation Board.

A day after the stalemate was reached, the Northern New England Passenger Rail Authority’s board decided Friday to put the matter back before the board, which officials hope will settle the matter once and for all.

The authority wants the Downeaster to run at 79 mph, but Guilford Rail Systems, which owns the track between Portland and Plaistow, N.H., contends the Amtrak train would be unsafe at that speed.

The Downeaster has been operating at 60 mph since service began in December, but Amtrak and the rail authority say it should be able to run at faster speeds.

Speed is important. The higher speed would shave 15 minutes off the Portland-to-Boston trip and increase its prospects for success, supporters say.

Guilford has contended all along that the rail authority should have used heavier rail during the track rehabilitation. Amtrak, the rail authority and the Federal Railroad Administration all maintained that passenger trains across the country operate safely on the 115-pound rail used in the track overhaul.

The Surface Transportation Board already intervened when the two parties became deadlocked on issues related to speed.

It directed the railroad authority to conduct tests of the rail, and those were conducted last year. Amtrak and the rail authority said its report by an independent consultant demonstrated that the average track modulus, a measure of track support, is double the criteria set by the Surface Transportation Board.

Guilford took issue with the findings at a meeting with Amtrak and the rail authority on Thursday in Billerica, Mass. The meeting ended with the two sides agreeing to disagree, said Michael Murray, executive director of the Northern New England Passenger Rail Authority.

The Downeaster went into operation on Dec. 15 with four daily trips in each direction between Portland and Boston.

Stops along the line include Saco and Wells in Maine; Dover, Durham and Exeter in New Hampshire; and Haverhill in Massachusetts. Seasonal stops in Old Orchard Beach will begin in June.