WASHINGTON (AP) — U.S. regulators are proposing to label insurer MetLife Inc. as a potential threat to the financial system, a designation that brings stricter government oversight. If the designation becomes final, MetLife would have to increase its cushion of capital against losses, limit its use of borrowed money and submit to inspections by examiners. The insurer argues that its industry is less risky than banking, and that imposing bank capital rules on life insurance companies would make it harder for Americans to buy insurance products.