All parties involved in the Iran nuclear deal agreed on Wednesday that the accord was working and that it should not be scrapped, said the European Union's foreign policy chief, Federica Mogherini.

"All parties are fulfilling the agreement," Mogherini told reporters at the United Nations General Assembly in New York, amid speculation that the US could be prepared to withdraw.

Read more: What are Donald Trump's objections to the Iran nuclear deal?

Although she could not guarantee that the US would remain part of the deal, she stressed that the EU was committed to preserving it.

Mogherini's comments came on the back of a meeting of top diplomats for the countries that negotiated and signed the nuclear accord with Iran in 2015 — China, France, Germany, Russia, the UK and the US.

The deal saw Iran agree to scale back its nuclear program in exchange for easing of sanctions and economic embargos.

Future of the deal? Trump's decided but won't tell

Wednesday's meeting marked the highest-level talks between US and Iranian officials since the beginning of the Trump administration.

Afterwards, US Secretary of State Rex Tillerson declared that, although Iran was in "technical compliance" with the accord, it was failing to live up to the expectations of the deal. Iran's continued support of the Syrian regime, its malicious cyber activity and ballistic missile development had fostered "anything but a more peaceful stable region," he said.

Trump called the nuclear accord "an embarrassment" to the US in his speech to the General Assembly on Tuesday, renewing fears he was considering withdrawing the US from an agreement he had repeatedly criticized as a presidential candidate.

Mixed signals from Trump and his ambassador to the UN, Nikki Haley, did little to calm those fears on Wednesday.

"It's not a clear signal that he plans to withdraw. What it is, is a clear signal that he's not happy with the deal," Haley told CBS News. 

US Secretary of State Rex Tillerson, who held talks with his Iranian counterpart Mohammad Javad Zarif on Wednesday, said that, while Iran was in "technical compliance" with the 2015 accord, it was failing to live up to expectations that the deal would remove a "serious threat" to the region.

Tillerson said that had Trump also already decided whether to withdraw from the deal, although the President would not share his decision with anyone "externally" before October 15, by which point he must make a decision.

The US top diplomat said the tone during his talks with Iran Foreign Minister Javad Zarif "was very matter of fact."

"We didn't throw shoes at one another. It was not an angry tone. It was a very, very matter of fact exchange," Tillerson said.

For his part, Trump, referring to the deal, said, "I don't think you've heard the last of it." He also said he had made a decision on whether to scrap the deal but would not share it with the public yet.

Trump is reportedly most upset about the accord's "sunset clause," which lifts restrictions on Iran's nuclear enrichment after 2025. 

Trump has until October 15 to decide whether Tehran is complying with the agreement. If he fails to do this, the US Congress has up to 60 days to decide to reapply the economic sanctions suspended by the agreement.  If US lawmakers reimpose economic sanctions the agreement would likely collapse.

Read more: What are Donald Trump's objections to the Iran nuclear deal?

Iranian President Rouhani: Tehran has 'various options' if US pulls out of nuclear deal

Iranian President Hassan Rouhani rejected any renegotiation of the 2015 nuclear deal and said Tehran had "various" options" if US President Donald Trump decides to pull the United States out of the agreement.

"This agreement is not something you can touch. If you take out a single brick, the entire building will collapse," Rouhani told reporters after a speech to the UN General Assembly on Wednesday. "An American government that chooses to trample on her legal and legitimate international commitments, a conversation with such a government would be a waste of time."

Should the United States pull out, Iran's "hand would be completely open to take any action that we see as beneficial to our country," Rouhani added. He did not elaborate on the comment but reiterated his country's claim to be seeking peaceful nuclear energy.

"Iran has never sought, is not now seeking and will never seek nuclear weapons," he said.

Iran promised to halt its nuclear program in 2015 as part of a deal with the five permanent UN Security Council members — the US, France, the UK, China, and Russia — and Germany. Leaders from those countries, who had previously expressed concern that Iran was striving to develop nuclear weapons, agreed in return to loosen economic sanctions on Iran.

During a speech earlier to the General Assembly, Rouhani warned the audience that "the Islamic Republic of Iran will not be the first country to violate the agreement." It would, he added, be "a great pity" if the deal were to be "destroyed by rogue newcomers to the world of politics."

US allies and adversaries rebuke Trump

France, Russia, and Germany, however, rejected Trump's criticisms , defending a deal that they claim has worked to bolster global security.

Russian Foreign Minister Sergey Lavrov said Trump's comments were "extremely worrying," according to the Russian Foreign Ministry. Lavrov said Russia would defend the accord that "was met with relief by the entire international community and genuinely strengthened both regional and international security."

Germany's leaders also made clear their opposition to any scrapping of the deal.

"Demolishing the nuclear deal with Iran would be a large step backward" and would be a "great danger to peace and stability in the region," Germany's foreign minister, Sigmar Gabriel, said at the UN. Berlin's top diplomat also said he hoped Iran would play a greater role in fostering a more peaceful Middle East.

In an interview with Deutsche Welle, German Chancellor Angela Merkel said the agreement was "better than having no agreement at all."

French President Emmanuel Macron told reporters in New York "it would be a mistake to annul the nuclear agreement without anything else." Macron said the deal "was a good one with strong monitoring of the current situation."

Macron also told reporters, however, that new "pillars" should be added to the agreement to improve it. These should include improved control of ballistic missile activities in Iran, lengthening the accord past 2025, when it is set to expire, and "open discussions with Iran about the current situation in the region."

Read more: Donald Trump and the Iran nuclear deal – a crisis in the making

Regional stability at risk

Saudi Foreign Minister Adel al-Jubeir signaled that his country, Iran's major rival for regional influence, wanted the pact strengthened, not jettisoned.

"We believe that it must be strictly reinforced. Iran has not lived up to the terms of the agreement," Jubeir told reporters. "We expect the international community to do whatever it takes to make sure Iran is in compliance with it."

Read more: Amid threats, Iran complies with nuclear deal, says UN watchdog

Since taking office, Trump's administration has repeatedly certified that Iran was meeting the conditions of the nuclear agreement — but officials in Washington also added they did not believe Tehran was meeting the "spirit" of the deal.

US allies in Europe, along with many of Trump's critics in Washington, fear this could trigger a new Middle East arms race and diplomatic crisis even as the world faces an aggressive nuclear-armed North Korea.

dm/rc (AP, AFP, Reuters)