CALGARY, Alberta (Reuters) - Royal Dutch Shell Plc has suspended production at its Canadian oil sands mine after environmental activists blockaded a massive dump truck and mining shovel to protest the impact of oil sands development, the company said on Tuesday.

Greenpeace said 25 of its activists locked down the oil sands mining equipment at the Albian Sands Muskeg River mine in northern Alberta on Tuesday morning, a day before Canadian Prime Minister Stephen Harper meets U.S. President Barack Obama in Washington.

Shell, which owns 60 percent of the 155,000 barrel a day operation, said it temporarily shut down mining to ensure that the activists and its staff do not get hurt.

“Shell’s No. 1 concern is their safety and our preference is for a negotiated end to this demonstration,” the company said in a statement. “We have invited the group into our administrative building to sit down with management to discuss their concerns.”

It said Greenpeace has not tried to contact Shell to discuss the environmental initiatives it is employing in the operation.

Greenpeace said it staged the protest to highlight what it said were “the climate crimes of tar sands development -- rising energy intensity, greenhouse gas emissions, and boreal forest destruction”.

The mine’s other owners are Chevron Corp and Marathon Oil Corp, with 20 percent each.

Elsewhere, activists hung a 70-foot (21-meter) banner above Niagara Falls on the Canada-United States border showing arrows that point forward to a “clean energy future” and backward to “tar sands oil”.