Ministers from Britain, China, France, Germany and Russian Federation met their Iranian counterpart in Vienna for the first time since U.S. President Donald Trump left a nuclear accord in May, but diplomats had seen limited scope for salvaging it.
They said they remained committed to the 2015 accord and to building up economic relations with Iran, including "the continuation of Iran's export of oil and gas" and other energy products.
Since Trump pulled Washington out of the historic nuclear deal, European countries have been scrambling to ensure that Iran gets enough economic benefits to persuade it to stay in the deal.
Iranian leader Hassan Rouhani embarked on a European tour this week in an attempt to salvage the multilateral nuclear agreement with EU leaders.
Maas said he expected negotiations to continue after the Friday talks, which were convened at Iran's request.
Hasn't Iran made this threat before?
Maas called the European offer "attractive" but conceded that "we won't be able to compensate for all the effects of enterprises withdrawing from Iran because they see their American business interests threatened by the sanctions".
"Unfortunately the proposed package lacked operational solution and specific method for cooperation, and featured just a set of general commitments like the previous statements by the European Union", the Iranian leader was quoted as saying on his official website.
French Foreign Minister Jean-Yves Le Drian said the signatories were trying to respond to "US extraterritorial measures aimed at companies that use the dollar for their commercial transactions".
Trump also said he would reinstate sanctions on Iran and impose "the highest level" of economic bans on the Islamic Republic.
Friday's developments came after Iran had voiced initial doubts about the other signatories' commitment on the eve of talks.
Rohani told French President Emmanuel Macron in a phone call that the package "does not meet all our demands", the IRNA state news agency reported late on July 5.
Iran, which strongly denies ever seeking to build a nuclear bomb, has warned it could resume uranium enrichment for civilian purposes if the deal collapses. Washington has since told countries they must stop buying Iranian oil from November 4 or face financial measures. Several major firms - including France's Total and Peugeot, and Russia's Lukoil - have said they are preparing to leave.
Meanwhile, Iran's representative to the Organization of Petroleum Exporting Countries, or OPEC, blamed Trump for rising oil prices, claiming that the president's rhetoric could force oil prices to rise to $100 per barrel.
Iranian protesters shout slogans during a demonstration in central Tehran on June 25, 2018.
Rouhani told Merkel the USA exit from the JCPOA has caused some problems in economic areas, banking transactions and oil sector for the foreign companies which have made investment in Iran, making them reluctant about continuing their operations in the country.