U. S. pressure has resulted in severed ties, stopped sales or scaled back business with Iranian firms, a growing number of companies worldwide have said.

The moves come as U. S. President Barack Obama seeks tough United Nations sanctions against Iran because, he and other Western leaders say, the country is seeking to develop the capability to build a nuclear weapon.

The U. S. accounting firms PricewaterhouseCoopers and Ernst & Young said they had cut off affiliation with Iranian firms, weeks after a similar decision by KPMG, the New York Times has reported.

The Times said that other companies that have reduced or ended business with Iranian firms include General Electric, Huntsman, Siemens, Caterpillar and Ingersoll Rand.

Daimler plans to sell a minority share in an Iranian engine maker, an Italian firm does not plan to renew its gas contract with Iran and the Malaysian state oil company cut off gasoline shipments to Iran, following the lead of others, including Royal Dutch Shell and Vitol.

Current and former U. S. officials told the Times that the companies' moves will help isolate Iran as it pursues its nuclear program.

Stuart Levey, the Treasury undersecretary, who leads the American effort to persuade firms to abandon Iranian ties, said, "No one of these actions is that significant. But the overall trend, if you analyze it with the increasing political isolation of Iran, could be very significant." (With Inputs from Agencies)