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Key U.S. European allies said in a joint statement Friday they were concerned after President Donald Trump vowed to end the Iran nuclear deal if Congress doesn't strengthen it.

"We encourage the administration and Congress to consider the implications to the security of the U.S. and its allies before taking any steps that might undermine the JCPOA, such as re-imposing sanctions on Iran lifted under the agreement," the statement said, using initials for the deal's official name, the Joint Comprehensive Plan of Action.

President Donald Trump walks past French President Emmanuel Macron (L) and German Chancellor Angela Merkel on his way to his spot for a family photo during the NATO summit at their new headquarters in Brussels, Belgium, May 25, 2017. Jonathan Ernst / Reuters

The American allies, however, said they share Trump's concern about Iran's ballistic missile program and aggression in the Middle East but insisted that maintaining the agreement is in their shared national security interests.

"We stand ready to take further appropriate measures to address these issues in close cooperation with the U.S. and all relevant partners," the countries said. "We look to Iran to engage in constructive dialogue to stop de-stabilizing actions and work towards negotiated solutions."

Other world leaders feared that Trump's approach to Iran could isolate America, strengthen economic rivals like Russia and China, and signal to North Korea that it's futile to negotiate with the Trump administration.

Sergei Alexeyevich Ryabkov, Russia's deputy foreign minister, called Trump's speech at the White House in which he laid out his Iran plan "extremely troubling" and said Moscow's main task now is to prevent the nuclear deal from collapsing.

Ali Larijani, the speaker of Iran's parliament, said if the U.S. withdraws from the deal, so will Iran.

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"They seem to have begun certain movements, which in the long run will cause a lack of order on the international arena," Larijani said on Friday, according to TASS, a Russian state news agency.

At the White House, Trump, who called the Iran agreement "one of the most incompetently drawn deals I've ever seen" earlier this week, said Iran was "not living up the spirit of the deal."

"In the event we're not able to reach a solution working with Congress and our allies, then the agreement will be terminated," Trump said.

Yukiya Amano, the director of the International Atomic Energy Agency, which oversees Iran's implementation of the deal, said in a statement that the country has been in compliance, despite Trump's claims on Friday that Iran has violated the deal multiple times.

"At present, Iran is subject to the world’s most robust nuclear verification regime," he said.

Russian Foreign Minister Sergey Lavrov KIRILL KUDRYAVTSEV / AFP - Getty Images

China said it hopes to preserve the Iran nuclear deal.

"We believe the Iran nuclear agreement has played an important role in safeguarding the international nuclear nonproliferation regime and safeguarding peace and stability in the Middle East," said Hua Chunying, a Foreign Ministry spokeswoman. "We hope all parties continue to preserve and implement the Iran nuclear agreement."

Israeli Prime Minister Benjamin Netanyahu, who has been warning about Iran's nuclear ambitions for years, praised Trump's speech, calling it "courageous."

"He boldly confronted Iran’s terrorist regime," Netanyahu said in a taped speech. "If the Iran deal is left unchanged, one thing is absolutely certain: In a few years’ time, the world’s foremost terrorist regime will have an arsenal of nuclear weapons and that’s a tremendous danger for our collective future."

He added: "President Trump has just created an opportunity to fix this bad deal. To roll back Iran’s aggression. And to confront its criminal support of terrorism."

The United Arab Emirates' ministry of foreign affairs also commended the speech in a statement, saying it welcomes the new strategy.

"The new U.S. strategy takes necessary steps to confront Iran’s malign behavior in all its forms," the ministry said.

Hassan Rouhani, the president of Iran, gave a scathing televised speech in response to the president's plan, calling it a "strategic mistake" and vowed a "strong and reciprocal reaction" toward the U.S. for the sanctions against the Islamic Revolutionary Guard, the country's hardline military wing.

"The claim by the president of United States regarding Iran's noncompliance has no international relevance or credibility," he said. "The U.S. president will have to bear full responsibility for all consequences of his rogue behavior."