WASHINGTON - The House voted yesterday to impose new economic sanctions on Iran as lawmakers cast doubt on Iran's willingness to respond to diplomatic efforts to curtail its purported nuclear-arms program.

The legislation, approved, 412-12, would end access to U.S. markets for foreign companies selling refined petroleum products to Iran or helping Iran develop its petroleum capacity. While Iran is a major crude oil producer, its inability to produce enough gasoline and other refined petroleum products is a major economic vulnerability.

All Philadelphia-area representatives voted in favor of the sanctions.

With no Senate action on the legislation expected this year, the House vote was for now mainly a warning that the United States is ready to act on its own if the Tehran government doesn't respond to international efforts to prevent Iran from becoming a nuclear power.

The bill drew opposition from lawmakers who said it would mainly cause hardship among poor and middle-class Iranians.

Deputy Secretary of State James Steinberg, in a letter to the Senate Foreign Relations Committee last week, said the Obama administration was "entering a critical period of intense diplomacy to impose significant international pressure on Iran." Sanctions legislation "might weaken rather than strengthen international unity and support for our efforts," Steinberg's letter said.

House Foreign Affairs Committee Chairman Howard Berman (D., Calif.) said Iran had had ample time to respond to President Obama's efforts at engagement.