The United States is paying a record $1.25 trillion annually in interest on its debt, equivalent to 18.5% of federal government revenue, according to analysis from DoubleLine. The figure exceeds the previous record of 18.4% set in 1991 and has more than quadrupled over the past four years. Billionaire Carlyle Group co-founder David Rubenstein said the United States has crossed a historical threshold at which debt-interest payments exceed national-security spending, calling that a sign of weakness. He said the country carries about $40 trillion in debt, pays more than $1 trillion in annual interest and spends about $1 trillion on national defense. Rising debt-service costs can crowd out defense, infrastructure and social safety-net spending while limiting the government’s ability to respond to future recessions. Rubenstein also said higher interest costs could push up borrowing costs for housing, credit cards and other loans, amid rising yields on 10-year and 30-year Treasurys.