Mogherini was speaking at a joint press point with Chinese Foreign Minister Wang Yi in Brussels on Friday following the EU-China strategic dialogue after the United States' move to withdraw from the nuclear agreement, officially known as the Joint Comprehensive Plan of Action (JCPOA), last month.
"Indeed, we are one hundred percent determined to continue cooperation between China and the European Union, but I can add also with Russia as it belongs to the signatory countries, but also with other partners internationally who are committed to preserve the nuclear deal and its full implementation," the senior EU official said.
Mogherini added that she held talks with the Chinese foreign minister on the "key" issue of the full continued implementation of the nuclear deal that has been the result of twelve long years of diplomatic work.
She noted that China played an "essential" role in the nuclear negotiations and would continue such its leading role in the upcoming weeks, months and years "in continuing the full implementation of the agreement."
The senior EU official stressed the importance of "the continued implementation of the nuclear-related commitments" under the JCPOA and said, "China's contribution here is relevant, key, and essential - in particular, the leading role that China has on the Arak [heavy water reactor] project."
In April 2017, Iran and China signed the final version of a contract to redesign and modernize the Arak heavy water reactor in central Iran, an important step in line with the implementation of the historic nuclear agreement between Tehran and the P5+1 group of countries.
According to the agreement, China is to review the new design of the Arak reactor made by the Iranian experts and confirm its compliance with the international safety standards of the International Atomic Energy Agency.
The 40-megawatt Arak reactor is intended to produce isotopes for cancer and other medical treatments. Iran is redesigning the planned research reactor to sharply cut its potential output of plutonium.
Mogherini further pointed to her talks with the Chinese foreign minister on bilateral cooperation on the economic aspects of the JCPOA implementation and urged "full coordination between China, the European Union and others in the world to guarantee that Iran can continue benefiting from the economic benefits that came from the agreement and will continue in the weeks to come."
She hailed "good" coordination between the sides on both the implementation of nuclear-related commitments and on the implementation of economic commitments of the nuclear deal.
"And the role of China, let me say it very clearly, has been and continues to be extremely crucial, positive and appreciated not only by the European Union, but also by our other partners," Mogherini pointed out.
US President Donald Trump announced on May 8 that Washington was walking away from the nuclear agreement, which was reached between Iran and the five permanent members of the UN Security Council - the US, Britain, France, Russia and China - plus Germany.
Trump also said he would reinstate US nuclear sanctions on Iran and impose "the highest level" of economic bans on the Islamic Republic.
Speaking to reporters in Brussels on Monday ahead of a meeting of EU foreign ministers, the European Union's foreign policy chief said the 28-nation bloc is determined to save the JCPOA despite the United States pullout from the deal.
She added, "You know that we have been acting already at European Union level to put in place a set of measures to make sure that the nuclear agreement is preserved and the economic investments from the European side, but also from other sides in the world are protected."
In a meeting with his Chinese counterpart in Beijing on May 13, Iranian Foreign Minister Mohammad Javad Zarif said he seeks a "clearer image" of the future of the key nuclear agreement after the US withdrawal.
During talks with the Chinese foreign minister, Zarif pointed to good relations between Tehran and Beijing after the JCPOA implementation started in 2016, adding, "We are confident that China will stand by Iran. China and Iran have comprehensive strategic partnership and are trade partners and these relations still continue."
