Trump's freewheeling remarks to reporters came after the president made the last-minute decision to call off an approved airstrike on Thursday
It is not yet clear whether the country is violating the terms of the Iran deal, known formally as the Joint Comprehensive Plan of Action (JCPOA).
Iran's leaders are demanding that their European counterparts do more to save the deal.
Britain's foreign secretary, Jeremy Hunt, urged Washington and Tehran to defuse tension to avoid destabilizing the Gulf region.
The same man who denounced the Iran nuclear pact as the "worst deal ever" is helping Iran's worst foe in the Persian Gulf get its feet on the nuclear ladder.
Iranian Foreign Minister Mohammad Javad Zarif said, "President Trump should've now realized that pageantries, photo-ops & flip-flops don't make for serious diplomacy."
Russian President Vladimir Putin's spokesperson said "sometimes we hear different statements from different agencies" in the U.S.
The drills were designed "to protect the territorial waters of our country, maintain lines of communication and promote the flag of the Islamic Republic of Iran."
The new special purpose vehicle for trade with Iran could keep the nuclear deal until 2020, experts argue.
The president has called his intelligence officials "extremely passive and naive" on foreign policy issues and suggested they should "go back to school!"
Both U.S. and Polish officials have argued that the conference would not target Iran, despite Secretary of State Mike Pompeo's statement that "there will be a focus on Iran."
The crown prince has threatened to develop nuclear weapons if Iran is able to do the same.
The European Union's foreign policy chief said the other nations would "protect the freedom of their economic operators."
"We deeply regret the re-imposition of sanctions by the U.S., due to the latter's withdrawal from the Joint Comprehensive Plan of Action," the foreign ministers of the EU, Germany, France and the U.K. said Monday.
Top diplomats from China, the EU, France, Germany, Iran, Russia and the U.K. believe the nuclear deal "is in the security interest of all."
Macron responded to Rouhani by saying that he "hoped that Iran, for its part, will fulfill its obligations without any ambiguity."
During his 2016 campaign Trump constantly referenced his skills as a businessman, but the president's first 16 months in the White House have been defined by an inability to work with Congress.
The EU's Federica Mogherini praised Beijing's efforts to save the deal.
Former Mossad chief Tamir Pardo said Israeli Prime Minister Benjamin Netanyahu's decision to potentially strike Iran may have been illegal.
Secretary of State Mike Pompeo accused Tehran of using Iran deal funds to back the Lebanese Shiite Muslim Hezbollah, as well as the jihadi Sunni Muslim groups.
The Justice Seekers Student Movement said the "illegal" building must be destroyed.