OTTAWA -- A dispute involving name tags sparked a slowdown Wednesday at the Ambassador Bridge border crossing in Windsor, Ont., the busiest trade link between Canada and the United States, and at the Blue Water Bridge crossing at Sarnia, Ont.

The Canada Border Services Agency says the disruption is the result of work refusals by several officers at those ports of entry.

By Wednesday afternoon, the agency was reporting no delays at the Windsor crossing while the Sarnia border post saw a minor delay for travellers only.

The union representing border guards says staff taking part in the job action are questioning the health and safety implications of wearing name tags on their uniforms.

"The officers will perform arrests and execute criminal warrants and so on. So having access to their name as opposed to their badge number is something we're very profoundly concerned with," said Ron Moran, national vice-president of the Customs and Immigration union.

In a memo to members dated Dec. 5, union president Jean-Pierre Fortin said the union "vehemently opposes" the new name tag policy.

He said the wearing of name tags exposes members to "unnecessary risks" and cautions members to "obey now, grieve later" to avoid any unnecessary discipline.

Public Safety Minister Vic Toews' office said border guards should wear name tags to ensure transparency.

Spokeswoman Julie Carmichael said guards shouldn't let their concerns tie up border traffic.

"We urge these workers to air their grievances in an appropriate manner -- not in a way that targets Canadian workers, travellers and Canada's economy," she said in an email.

The agency says, however, that name tags are in line with similar policies in place in the Canadian Forces, Correctional Service Canada and United States Customs and Border Protection, whose frontline uniformed officers all wear name tags.

Fortin, the union president, wrotes in his email to members that legal counsel is examining the name tag requirement as the union considers its options.

He also advised any members whose names are visible to the public to consider removing their names from social media, telephone listings and other directories.

The CBSA says in a statement that management will closely monitor border traffic and try to resolve any unwarranted delays, adding that any illegal actions and inappropriate behaviour "will be dealt with accordingly."

The CBSA says it encourages travellers to check border wait times on the CBSA website.