OTTAWA -- The two men seeking to replace Stephen Harper as prime minister are focusing on security and safety, one day after the Conservatives announced changes to more quickly bring Syrian refugees to Canada this year.

The Liberals and NDP have both promised to bring in more refugees this year than the Tories, with Justin Trudeau suggesting that Canada provide airlifts to refugees fleeing the violence in Syria.

The Liberal leader made the comments in Halifax where he vowed to save taxpayers "tens of billions of dollars" by scrapping the controversial purchase of the F-35 fighter jet -- only to be peppered with questions about his plans for Canada's military.

Campaigning in St. John's, N.L., NDP Leader Tom Mulcair talked up his party's promises to increase spending on social programs before vowing to reopen a maritime rescue centre in the city and reinvest in coast guard search and rescue.

The renewed opposition focus on defence, security and foreign affairs comes one week before Harper, Mulcair and Trudeau meet for a federal leaders' debate on that very topic.

Green party Leader Elizabeth May hasn't been invited to that debate. Her party has filed a complaint with the Canada Revenue Agency, arguing that the exclusion amounts to a violation by the debate's sponsor of the Income Tax Act, which prohibits charitable foundations from supporting or opposing political parties.