While prices on the bonds are holding near 80 cents on the dollar, saving creditors from the losses that typically follow a default, and the peso and local interest rates remain stable, Argentina is showing some concern that the situation may deteriorate by taking steps to preserve hard currency. The tax agency has slowed the pace of import approvals, adding to a $4 billion backlog that is equivalent to 67 percent of all of June’s imports, according to Jose Alfredo Nogueira, director of ABC Mercado de Cambios, a Buenos Aires-based currency dealer.