Thwarted internationally, the Obama administration cobbled together a new set of best-available sanctions against Iran on Monday that underlined its limited capacity to force Tehran to halt its suspected nuclear weapons program. The U.S. action was coordinated with Britain and Canada, but not with countries such as Russia and China that have far greater economic investments in the Islamic republic. The American sanctions target Irans oil and petrochemicals industry and Iranian companies involved in nuclear procurement or enrichment activity. The U.S. also declared Irans banking system a center for money laundering designed as a stern warning to financial institutions around the world to think twice before doing business with Tehran. President Barack Obama said Iran had a choice: come clean on its nuclear program and reap the benefits of closer economic cooperation with the world, or face even more pressure.