A 12-metre swath cut through the forest defines the border between Canada and the U.S. north of Polebridge, Mont. (Jennifer DeMonte/Daily Inter Lake/Associated Press )

The United States is looking at building fences along the border with Canada to help keep out terrorists and other criminals, according to a draft report by the U.S. Customs and Border Protection agency

The report proposes the use of "fencing and other barriers" on the 49th parallel to manage "trouble spots where passage of cross-border violators is difficult to control."

But a spokesperson for U.S Customs and Border Protection said the government is not considering the fence option "at this time" and instead is looking at the environmental effects of putting more manpower, technology and infrastructure along the border.

The border service is also pondering options including a beefed-up technological presence through increased use of radar, sensors, cameras, drones and vehicle scanners. In addition, it might continue to improve or expand customs facilities at ports of entry.

The agency considered but ruled out the possibility of hiring "significantly more" U.S. Border Patrol agents to increase the rate of inspections, noting staffing has already risen in recent years.

Customs and Border Protection is inviting comment on the options and plans a series of public meetings in Washington and several U.S. border communities next month. It will then decide which ideas to pursue.

U.S. Homeland Security Secretary Janet Napolitano noted last month the challenges of monitoring the vast, sparsely populated northern border region. She stressed manpower, but also a greater reliance on technology.

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Ironically, the moves come as Canada and the U.S. try to finalize a perimeter security arrangement that would focus on continental defences while easing border congestion. It would be aimed at speeding passage of goods and people across the Canada-U.S. border, which has become something of a bottleneck since the 911 attacks.

Relatively speaking, Washington has focused more energy and resources on tightening security along the border with Mexico than at the sprawling one with Canada.

But that may be changing.

Only small portion secured

A U.S. Government Accountability Office report recently warned that only a small portion of the border with Canada is properly secure. It said U.S. border officers control just 50 kilometres of the 6,400-kilometre boundary.

The Customs and Border Protection report says while fences have been a big element in deterring unauthorized crossings of the U.S.-Mexican border, "it is unlikely that fencing will play as prominent a role" on the northern border, given its length and terrain that varies from prairie to forest.

However, the agency would use fencing and other barriers such as trenches to control movement and sometimes delay people trying to sneak across the border, increasing the likelihood they could be caught, says the report.

It doesn't provide details about what the fences might look like, but suggests they would be designed to blend into the environment and "complement the natural landscape."

The approach would also involve upgrading roadways and trails near the border.

"The lack of roads or presence of unmaintained roads impedes efficient surveillance operations," says the report. "Improving or expanding the roadway and trail networks could improve mobility, allowing agents to patrol more miles each day and shortening response times."

Over the last two years, the U.S. Department of Homeland Security has already made what it calls "critical security improvements along the northern border," adding inspectors at the ports of entry and Border Patrol agents between ports, as well as modernizing land crossings.

Nearly 3,800 Customs and Border Protection officers scrutinize people and goods at crossings. The number of Border Patrol agents working between crossings along the northern parallel has increased 700 per cent since Sept. 11, 2001. And some three dozen land ports of entry are being modernized.

Unmanned U.S. aircraft patrol about 1,500 kilometres along the northern border from Washington to Minnesota as well as more than 300 kilometres of the Canadian border around New York state and Lake Ontario.