OTTAWA -- The federal border agency is bowing to privacy concerns by agreeing to slash the amount of time it will keep data on the cross-border movements of Canadians as part of a new security plan.

The Canada Border Services Agency says it plans to retain personal details gleaned from the Canada-U.S. initiative for 15 years -- not 75 -- following pressure from the federal privacy watchdog.

The tracking system involves exchanging entry information collected from people at the land border -- so that data on entry to one country would serve as a record of exit from the other.

The federal government plans to use the data for purposes ranging from catching unemployment insurance cheats to ensuring people ineligible to stay in Canada have left the country.

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

The program was to be expanded next Monday to include information sharing on all travellers. In addition, Canada hoped to begin collecting information on people exiting by air -- something the United States already does -- by requiring airlines to submit passenger manifest data for outbound international flights.

The government says the airline data could help identify sex offenders planning to travel abroad or extremists off to join foreign conflicts such as the one raging in Syria, where young Canadians have already been killed.

The government's June 30 deadline for those elements will be missed because legislative and regulatory changes still need to be made, federal and industry officials say.

The entry-exit initiative is a key element of the highly touted perimeter security deal intended to help ease the passage of travellers and cargo across the Canada-U.S. border while bolstering continental security.

Preliminary results of the second phase of the initiative, which began early last summer, demonstrate the program "is working as intended," say border agency briefing materials obtained by The Canadian Press under the Access to Information Act.

For the period June 30 to Sept. 30, 2013, 1.29 million entry records were received from the United States and Canada sent 1.34 million to the Americans.

A comparison of the data against the databases of Canada's border agency revealed that 20 people subject to active immigration warrants or removal orders had left Canada, say the materials prepared last November. At last count, that led to four warrants being cancelled.

The privacy commissioner's office had expressed concern about plans to keep information for 75 years and asked the border agency to review the "lengthy retention period."

For future phases, Canada will keep personal information on all travellers for 15 years in "personalized" form and for another 15 years stripped of personal details, for a total of 30 years, the briefing notes say.

The privacy watchdog's office is pleased with the development, spokeswoman Valerie Lawton said Wednesday.

Still, it has asked the border agency to provide a justification for the newly proposed retention period when it submits detailed privacy assessments of the program's next stages, she said.

However, the U.S. has indicated it plans to keep information collected under the program for anywhere from 15 to 75 years -- or possibly longer -- depending on the circumstances.

The Canadian border agency sent a letter to the acting chief privacy officer of the U.S. Department of Homeland Security recommending signs be posted at U.S. land border crossings -- as Canada had done on its side of the border -- informing travellers of the data collection.

Homeland Security did not respond to questions about the next phase of the project.

The Canada Border Services Agency confirmed that "legislative and regulatory changes are required" before the full exchange of data on Canadian and American travellers takes place.

Additional information on the proposed changes will be provided "when legislation is tabled," border agency spokeswoman Patrizia Giolti said in an email response to questions.

It is difficult to gauge the usefulness of the cross-border information exchanges or to know if the privacy protections will prove adequate, said Christopher Sands, a senior fellow at the Washington-based Hudson Institute, an independent research organization.

"We haven't really got any evidence one way or the other about how this data is being used and whether there's any sort of problem."