PARIS - France, Germany and the UK regret the US decision to leave the JCPOA (Joint Comprehensive Plan of Action)," French President Emmanuel Macron, a champion of the Iran nuclear deal, wrote on Twitter. "The nuclear non-proliferation regime is at stake," he added.
"We will work collectively on a broader framework, covering nuclear activity, the post-2025 period, ballistic activity, and stability in the Middle East, notably Syria, Yemen and Iraq."
His Foreign Minister, Jean-Yves Le Drian, said in a radio interview "the deal is not dead". He said Europe's foreign leaders will meet next week with representatives from Iran to talk about the future of the JCPOA.
Germany also reiterated it also wants to uphold the deal. Foreign Minister Heiko Maas said "the deal makes the world safer", adding that Germany could find no legitimate reason for pulling out of the deal.
On Twitter, UK Foreign Minister Boris Johnson said he regretted the US no longer taking part in the nuclear deal.
"UK remains strongly committed to the JCPoA, and will work with E3 partners and the other parties to the deal to maintain it," he added.
The top European Union diplomat, Federica Mogherini, called on the international community to preserve the Iran nuclear deal.
"The EU will remain committed to the continued full and effective implementation of the nuclear deal," Mogherini said from Brussels.
"We fully trust the work, competence and autonomy of the International Atomic Energy Agency that has published 10 reports certifying that Iran has fully complied with its commitments.
"The lifting of nuclear-related sanctions is an essential part of the agreement. The EU has repeatedly stressed that the lifting of nuclear-related sanctions has a positive impact not only on trade and economic relations with Iran, but also mainly, [it has] crucial benefits for the Iranian people."
China, one of the countries that signed the JCPOA, joined the Europe its response, saying the country is committed to protecting the deal as it stands.
China's special envoy to the Middle East, Gong Xiaosheng, said in a press conference in Iran the agreement promoted peace.
"Having a deal is better than no deal. Dialogue is better than confrontation." he said according to Xinhua news agency.
Russia, one of the signatories of the deal, said it will try to keep the deal functioning despite Tuesday's decision by the US.
Yevgeny Serebrennikov, first deputy head of the defense and security committee in the Russian Upper House of Parliament also told RIA news agency Trump's decision could put the nuclear talks between the US and North Korea at risk.
Former US president Barack Obama whose administration negotiated and signed the deal, issued a list of points why Trump's decision is "so misguided". "The reality is clear. The JCPOA is working - that is a view shared by our European allies, independent experts, and the current US Secretary of Defence," Barack Obama wrote.
"The JCPOA is in America's interest - it has significantly rolled back Iran's nuclear programme. And the JCPOA is a model for what diplomacy can accomplish - its inspections and verification regime is precisely what the United States should be working to put in place with North Korea.
"Indeed, at a time when we are all rooting for diplomacy with North Korea to succeed, walking away from the JCPOA risks losing a deal that accomplishes - with Iran - the very outcome that we are pursuing with the North Koreans."
John Kerry, Obama's former US secretary of state said: "Today's announcement weakens our security, breaks America's word, isolates us from our European allies, puts Israel at greater risk, empowers Iran's hardliners, and reduces our global leverage to address Tehran's misbehaviour, while damaging the ability of future Administrations to make international agreements."
"No rhetoric is required. The facts speak for themselves. Instead of building on unprecedented nonproliferation verification measures, this decision risks throwing them away and dragging the world back to the brink we faced a few years ago.
"The extent of the damage will depend on what Europe can do to hold the nuclear agreement together, and it will depend on Iran's reaction. America should never have to outsource those stakes to any other country. This is not in America's interests. We should all hope the world can preserve the nuclear agreement."
Australia and Japan have also said they regret the US decision. Australia's Prime Minister Malcolm Turnbull called on all sides to use restraint in their response.
Japan's Foreign Minister Taro Kono issued a statement saying Japan hopes the pulling out does not affect Iran's capabilities of adhering to the JCPOA.
"We hope that the countries involved will continue to deal with the issue in a constructive manner," he added.
Turkey called Trump's decision "an unfortunate step", adding that the deal was an important step to prevent nuclear proliferation.
"The Joint Comprehensive Plan of Action must be protected and continue to be implemented in full transparency, uninterrupted and complete, under the control of the IAEA," a statement on the foreign ministry's website said.
Ibrahim Kalin, spokesperson for President Recep Tayyip Erdogan, said on Twitter the US withdrawal could put the world at risk.
"Turkey maintains its firm stance against all nuclear weapons regardless of who owns them,", he added.
The 2015 agreement curbed Iran's nuclear activities in return for the lifting of sanctions that had been imposed by the UN, US and EU.
But Mr Trump argued that the deal was "defective at its core", saying he would pull out and reimpose sanctions.
Other signatories to the nuclear accord say they remain committed to it.
The deal was agreed between Iran and the five permanent members of the UN Security Council - the US, UK, France, China and Russia - plus Germany. It was struck under Mr Trump's predecessor, Barack Obama.
Iran said it would try to salvage the agreement, but would restart uranium enrichment if it could not.
In a statement, President Hassan Rouhani said: "If we achieve the deal's goals in co-operation with other members of the deal, it will remain in place.(FA)