Canada's border agency has quietly begun sharing information with U.S. Homeland Security about the thousands of American citizens who cross into Canada each day.

Before long, Washington is expected to provide Ottawa with similar information about Canadians entering the United States.

The exchanges are intended to bolster security and help enforce laws, though advocates for privacy and civil liberties are concerned about the potential for abuse.

Canada says it will use the data for everything from zeroing in on suspected terrorists to ensuring people are actually entitled to social benefits they're collecting.

Under a 2011 continental security pact, Canada and the United States agreed to set up co-ordinated systems to track the entry and exit information of travellers.

The effort involves exchanging entry information collected from people at the land border — so that data on entry to one country serves as a record of exit from the other.

The data includes the traveller's name, nationality, date of birth and gender, the country that issued their travel document and the time, date and location of their crossing.

The first two phases of the program were limited to foreign nationals and permanent residents of Canada and the U.S., but not citizens of either country.

Canada introduced legislation in June 2016 to implement the next phase of the data-collection system. But that bill has not moved beyond first reading in the House of Commons. As a result, information on Canadian citizens is not yet being shared.

However, the two countries agreed last year, as an "interim step," to expand the initiative to include the passage of information to the U.S. from Canada on all American citizens, records disclosed under the Access to Information Act show.

Tracking fugitives, sex offenders

Canada and the U.S. signed a memorandum of understanding in August 2016 that allows American officials to disclose the border-crossing data about U.S. citizens to "any federal, state, local or tribal government authority" in the U.S. for reasons of national security, counter-terrorism, public health or safety.

Similarly, Canada wants such data to track the departure plans of known fugitives, suspected terrorists and registered sex offenders, respond more effectively to missing-child alerts and identify people who overstay their time in Canada.

The government says the information will also focus immigration enforcement on people in Canada, as opposed to those who have already left and help determine entitlement to social benefits, which may require a presence in Canada.

Concerns over privacy

The planned data exchanges go too far in monitoring the travel patterns of Canadians who have not broken any laws and the information could be used to build invasive personal profiles, said Tim McSorley, national co-ordinator for the Ottawa-based International Civil Liberties Monitoring Group.

That's worrisome, he said, because most people who cross the border assume it's a check to make sure there is no warrant for their arrest and that they're not carrying contraband. "But not that their movements are being recorded and retained in a database."

In response to questions, the Canada Border Services Agency said it "takes privacy seriously" and has consulted the federal privacy commissioner's office throughout development and implementation of the project.

It said once the legislation before Parliament receives royal assent, an updated privacy assessment will be provided to the commissioner.

The agency called the interim provision of information on U.S. citizens "another step forward" in ensuring a secure and efficient border.