Canadian Prime Minister Justin Trudeau defended Wednesday a government bill that would increase the power of U.S. border agents to question and detain U.S.-bound travelers at Canadian airports and other crossings. Trudeau also said Canada will still protect travelers in Canada even if they are detained for more questioning or a search by American authorities in a preclearance zone.

But critics such as Canada's New Democrats Party argued the bill doesn't take into account what it called "the climate of uncertainty at the border" since President Donald Trump took office in January and vowed to deport millions of immigrants. The White House's policies have seen more people cross the border to get into Canada in recent weeks and Trump has vowed to heavily probe travelers coming into the U.S. The fear is that Canadians traveling to the U.S. could soon face a harder process under Trump.

The bill will enact an agreement between the U.S. and Washington signed in 2015 to expand border clearance and speed the flow of people and goods across the border by setting up new U.S. customs facilities in Canadian airports. Under the policy, travelers don't have to pass through customs in the U.S., because they've already done so before departing Canada. The expanded policy will allow American customs agents to carry weapons within Canada, perform body searches and detain travelers. 

"If we didn't have preclearance in Canada, people would be passing customs in the United States. And in the United States, American laws dominate and control the behavior of people in border crossings. When you're doing preclearance in Canada, the Canadian Charter of Rights and Freedoms and Canadian laws are in place, so there is extra protection," Trudeau said.

Canada has allowed U.S. customs officials on its soil for decades. Canada's Public Safety Minister Ralph Goodale said this week the new expanded program will further protect and serve Canadians.

“Getting all those customs and immigration processes out of the way before you board the plane or before you cross the border, doing it on Canadian soil under Canadian law under the Canadian Charter of Rights and Freedoms – that’s a massive advantage for Canadians,” he said.

Trudeau also said Tuesday Canada will continue to accept undocumented refugees crossing the border from the United States despite opposition from conservative lawmakers.