A former head of the U.S. Department of Homeland Security calls it "regrettable" that Canada plans to withdraw from the conflict in Afghanistan.

Michael Chertoff, former head of the U.S. Department of Homeland Security, speaks with journalists on Feb. 25, 2009, on the sidelines of the Bahrain Security Forum in Manama, Bahrain. (Hasan Jamali/Associated Press) "The consequences of failure in this part of the world will not be limited to the United States," said Michael Chertoff, who served from 2005 to 2009 in the administration of former president George W. Bush.

"They will be felt by everybody," Chertoff said in an interview broadcast Wednesday on The Current with Anna Maria Tremonti.

"Support by our NATO allies is a very, very important element of the strategy [in Afghanistan]."

Chertoff said he strongly supports President Barack Obama's buildup of U.S. troops in Afghanistan. If an "enduring infrastructure" is not established in that country, Chertoff believes extremists will regain control of large chunks of territory,

"That's exactly what put us into the situation we had prior to 9/11," he said. "The consequences of that will be felt not only in the United States but in Canada and around the world."

Chertoff believes the challenge of this century is "ungoverned space," where there is no government that can maintain order. Those areas of the world can give terrorists room to thrive, he said.

"It would be very short-sighted to stint on the investment now and face the consequences in five years," he said. "So I think President Obama is dead-right in what he is doing."