U.S. DUBAI, Sept 6 (Reuters) - Iran said it will step up efforts to tackle problems created by the U.S. Key points and original sources are listed below.

• U.S. Central Command hit three Iranian tankers on Saturday in response to strikes on two U.S. Navy ShipsS1

• DUBAI, Sept 6 (Reuters) - Iran said it will step up efforts to tackle problems created by the U.S. sanctions that are crippling its economy, while a senior Iranian official warned of a "painful response" if it comes under further attack.Six months after U.S.-I...S2