A proposal under consideration would temporarily waive a requirement that U.S. passports be used for air travel to and from Canada and Mexico, provided the traveler can prove he or she has applied for a passport. The officials say the proposed six-month suspension in the rules is aimed at clearing a massive backlog of passport applications at the State Department, however the plan has run into opposition from the Homeland Security Department, which fears the move could make it easier for terrorists or other undesirables to enter the country. Some officials say an announcement of the change could come as early as today.