However, Rouhani told French President Emmanuel Macron by telephone on Thursday that the package of economic measures failed to offset sufficiently the effects of the US pullout and its re-imposition of nuclear-related sanctions.
The top Iranian diplomat said the participants at the Vienna meeting agreed to take "good measures" to save the JCPOA.
Germany's foreign minister said on Friday world powers would not be able to fully compensate for companies leaving Iran due to new US sanctions, but warned Tehran that abandoning its nuclear deal would cause more harm to its economy.
Rouhani made the remarks in a telephone conversation with German Chancellor Angela Merkel late on Thursday.
Zarif pointed to his "very serious and constructive" talks with the remaining parties of the nuclear deal and said, "I believe that there is political will to continue work and save this agreement but we must see what will happen to this issue in practice."
Besides, Commander of the IRGC Quds Force Qasem Soleimani on Tuesday lauded Rouhani for responding strongly to a USA plan aimed at blocking Iran's oil sales, saying "this is the Dr. Rouhani we used to know and the one he should be".
While the other signatories have vowed to stay in the accord, dozens of European, Russian, and Asian companies have announced plans to pull out of Iran for fear of incurring USA penalties when sanctions are reimposed in November. He promised to reinstate the previous anti-Iranian sanctions and even impose tighter ones.
Iranian officials have said that key for them is to ensure measures that guarantee oil exports do not halt, and that Tehran still has access to the SWIFT global bank payments messaging system or an alternative.
Rouhani warned Wednesday that Iran could reduce its cooperation with the United Nations' nuclear watchdog if the nuclear deal falls apart.
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The U.S. Navy stands ready to ensure free navigation and the flow of commerce, the U.S. military's Central Command said on Thursday, as Iran's Revolutionary Guards warned they would block oil shipments through the Strait of Hormuz if necessary.
German Foreign Minister Heiko Maas also said that world powers would not be able to fully compensate for companies who are abandoning their operations in Iran.
Rohani did not specify what he found lacking in the European Union package of measures to counter US sanctions.
Reuters reports that whether the bank will invest in Iran is in doubt.
Also, the bank has expressed concerns that it will have difficulty raising money in financial markets if it defies the USA sanctions.
Beyond the European Investment Bank plan, other elements of the European economic package that Rohani criticized as insufficient include a special measure to shield EU companies from the US sanctions and a proposal for EU governments to make direct money transfers to Iran's central bank to avoid USA penalties.
Trump pulled the United States out of the multinational deal under which sanctions on Iran were lifted in return for curbs on its nuclear programme verified by the International Atomic Energy Agency (IAEA).
Other objectives Mogherini outlined included maintaining wider economic relations with Iran, financial channels, Iran's export of oil and gas, and the continuation of sea, land, air and rail transportation links.
Since Trump's announcement, Iran's rial currency has fallen, prices have risen and the country has been hit by street protests and strikes.