President Donald Trump gave European partners an ultimatum Friday to fix "significant flaws" in an Iranian nuclear agreement, or he will withdraw the United States from the deal in a few months' time.

"This is a last chance," Trump said as he extended sanctions waivers on Iran in accordance with the multilateral agreement his predecessor Barack Obama signed in 2015.

"I hereby call on key European countries to join with the United States in fixing significant flaws in the deal, countering Iranian aggression and supporting the Iranian people," Trump said in a statement.

"If other nations fail to act during this time, I will terminate our deal with Iran," he said.

In July 2015, Iran and six major powers -- Britain, China, France, Germany, Russia and the United States -- struck an accord formally called the Joint Comprehensive Plan of Action in which Iran pledged to curb activities such as uranium enrichment.

To fix what he described "disastrous flaws" in the deal, Trump demanded that Iran be denied "all paths to a nuclear weapon not just for 10 years, but forever," and that Tehran allow "immediate inspections at all sites requested by international inspectors."

In Tehran, Iranian Foreign Minister Javad Zarif condemned Trump for "maliciously violating" the nuclear agreement. Iranian officials have said they are not interested in any renegotiation.

Speaking to reporters earlier Friday, a senior U.S. administration official said Trump will seek "a follow-on or a supplemental agreement" with European partners to strengthen the deal he has vowed to scrap.

Separately, the Treasury Department said it imposed sanctions on 14 individuals and entities from Iran, China and Malaysia over Tehran's human rights abuses and ballistic missile development.

"We are targeting the Iranian regime, including the head of Iran's judiciary, for its appalling mistreatment of its citizens, including those imprisoned solely for exercising their right to freedom of peaceful assembly, and for censoring its own people as they stand up in protest against their government," Treasury Secretary Steven Mnuchin said.

"We are also targeting Iran's ballistic missile program and destabilizing activities, which it continues to prioritize over the economic well-being of the Iranian people," Mnuchin said in a statement.