U.S. retail sales rose less than expected in June, the government reported Monday, adding to indications of a slowdown in economic growth. The Commerce Department said retail sales rose 0.4 percent last month after a 0.5 percent gain in May. Economists had forecast retail sales, which account for about 30 percent of consumer spending, to rise 0.8 percent. While Americans spent more at retail businesses in June, the gain was mostly driven by auto sales and higher gasoline prices. Auto sales jumped 1.8 percent last month, the biggest gain since November. Higher gasoline prices pushed service-station sales up 0.7 percent. Excluding autos, retail sales were flat in June after rising 0.3 percent the previous month. Excluding the volatile categories of autos, gasoline, and building materials, core retail sales - which correspond most closely with the consumer-spending component of gross domestic product (GDP) - rose only 0.15 percent in June, the weakest reading since January. The signs of slower domestic demand, as well as weak trade and manufacturing data, come as the Federal Reserve (Fed) is debating a slowdown in its monthly $85 billion purchase of bonds, intended to keep long-term interest rates low and stimulate the economy.