Oil giant Shell and chemicals firm BASF are to sell their joint plastics making venture Basell to a group of investors for 4.4bn euros ($5.7bn; £3bn).
US officials expressed concerns over a possible Iranian deal
News of the deal comes a day after Iran's National Petrochemical Company said US political pressure had excluded it from buying the Dutch firm.
The US State Department had raised concerns over a possible Iranian deal.
Basell will now be sold to US-based investors Access Industries and The Chatterjee Group.
Iran's state-owned National Petrochemical Company said on Wednesday that, despite winning a tender for Basell, pressure from Washington had blocked any deal.
The US State Department said it had contacted Shell and BASF to express concern over the possible misuse of Basell technology should an Iranian takeover take place.
Under US sanctions rules, US companies would no longer be able to trade with Basell if the Iranian firm was successful, the State Department said.
Iran was one of the countries listed by President George W Bush as belonging to an 'axis of evil' in a speech in 2002.
Anglo-Dutch Shell and Germany's BASF expect to gain 1bn euros each from the deal, once debt considerations are taken into account.
Basell is the world's biggest producer of polypropylene, which is used in a range of applications from car dashboards to packaging.