Europeans are accusing Americans of strong-arming them into cracking down on Iran in the latest trans-Atlantic conflict straining efforts to maintain a joint front on Teheran and its refusal to freeze uranium enrichment.
US officials, in turn, complain that Europe is not pulling its weight because individual nations are placing business interests above the common goal of keeping Iran from heading down a path that could lead to nuclear weapons.
State Department spokesman Shawn McCormack has said that Washington would "continue to push and prod" the Europeans.
US companies are barred from doing business with Iran, and a law Congress passed in 1996 allows Washington to penalize even foreign firms engaged in commerce with the Islamic republic.
EU foreign ministers called on all countries to enforce sanctions outlined in a UN resolution last month that targeted people and programs linked to Iran's nuclear and ballistic missile programs. But there is nothing comparable to the US legislation in the European Union.
European officials say nothing obliges their countries to follow US footsteps and choke off trade and economic ties with Iran beyond what is stipulated in the UN resolution.
The American measures "have no effect for the European people," French Foreign Ministry spokesman Jean-Baptiste Mattei told reporters last week.
That does not stop the Americans from trying.
European officials and industry representatives told The Associated Press of increased calls by US Treasury or embassy officials on European banks, oil companies and other sensitive industries in recent weeks to get them to cut back on dealings with Iran.
"All the oil companies will tell you that they are having regular visits from the US embassies in their countries," said a European oil consultant, speaking on the sidelines of last week's Vienna meeting of the National Iranian Oil Co. with international oil firms seeking to do business with OPEC's second-largest producer of crude.
Roughly 80 percent of Iran's revenues come from oil exports - and Teheran's creaky oil industry badly needs foreign investment to keep up production and export. So it makes sense for Washington to keep up the pressure on the oil front.
The US Embassy in Vienna acknowledged Washington encourages "companies to consider whether such investments will really be stable over the long term, and whether they will be worth the risk to their investments and to their international reputations." With America shut out of Iran, oil companies from other countries remain eager to take up the slack, particularly because Teheran's petroleum industry is not under UN sanctions.
Though it has fallen since then, total European Union trade with Iran was at more than US$25.85 billion in 2004, the last year complete figures were available.
Among those signed up for the Vienna meeting were executives from Russia's Lukoil, China's Sinopec, Austria's OMV and Royal Dutch Shell PLC.
"Nobody in Europe is going to give up the opportunity of doing business with Iran just for the sake of pleasing the Americans," the oil consultant said.
Such attitudes clearly rankle US officials.
Gregory L. Schulte, the chief US representative to the International Atomic Energy Agency, called on European governments Wednesday to stop granting credits "to subsidize exports to Iran," and to "take more measures to discourage investment and financial transactions." If anything, the trans-Atlantic strains could increase.
"What we are not going to do is mirror what the (US) Federal Reserve has done," the official said, alluding to US moves to freeze designated Iranian assets, including some big banks.
Russia - a veto-wielding Security Council member that backs calls for an end to Iranian enrichment but was the key opponent of a US push for harsher UN sanctions - complicates the mix by maintaining multibillion-dollar business ties with Iran that irritate both Washington and Brussels. Commerzbank last week ended dollar-demoninated transactions with Iran, after officials at the bank - Germany's second-largest - spoke of "US pressure" on their institution. With the move, Commerzbank joined Britain's Barclays PLC and HSBC Holdings PLC, Societe Generale SA and Credit Lyonnais of France, and Credit Suisse Group, UBS AG and ABN Amro Holding of Switzerland.