U.S. President Donald Trump (Xinhua file photo)

WASHINGTON, Jan. 12 (Xinhua) -- U.S. President Donald Trump said on Friday he will extend sanctions relief on Iran under the 2015 nuclear deal for the last time, threatening a U.S. withdrawal from the landmark pact unless U.S. Congress and European allies can fix the alleged "disastrous flaws."

Calling it "a last chance," Trump said in a White House statement that his country "will not again waive sanctions in order to stay in the Iran nuclear deal."

Responding to Trump's harsh stance, Iranian Foreign Minister Mohammad Javad Zarif said on Friday that it was "desperate attempts" to undermine an accord which Iran said was "not renegotiable."

"Trump's policy & today's announcement amount to desperate attempts to undermine a solid multilateral agreement," said Zarif on Twitter.

Trump has long been critical about the pact inked between the six world powers, namely China, Russia, Britain, France, the United States and Germany, and Iran in 2015, in which the West promises to relieve sanctions on Tehran in exchange for a halt in Iran's efforts to develop a nuclear weapon.

The U.S. president must sign a waiver suspending the U.S. sanctions on Iran every 120 days.

Calling it "one of the worst" deal the United States has ever made, Trump, who has signed the waiver twice since taking office, decertified to Congress Iran's compliance with the pact last October.

The United States is the only party that has threatened to scrap the deal, a stance that has been confronted by other participants.

On the eve of Trump's announcement, diplomats from Britain, France, Germany and the European Union again called on Trump to uphold the pact.

French President Emmanuel Macron emphasized the importance of abiding by the deal "in order to guarantee better stability in the Middle East," according to a readout of his telephone conversation with Trump on Thursday.

Meanwhile, China and Russia, the other two parties, have also repeatedly called on the United States to maintain its commitment to the Iranian Nuclear deal which is "a beneficial practice of solving a critical issue through political and diplomatic means."

As Trump agreed to the sanctions relief, U.S. Department of Treasury said on Friday that it has imposed new sanctions on 14 individuals and entities over Iran's alleged human rights abuses and ballistic missile program, including head of Iran's judiciary and the cyber unit of the Islamic Revolutionary Guard Corps.

The U.S. has sanctioned around 100 individuals and entities involved with Iran's ballistic missile program and other activities which the United States saw as "illicit," according to Trump's statement on Friday.

In the statement, Trump also laid out conditions to the Congress and the European allies for a fix to the deal to keep America in it.

White House is working with Congress on a U.S. legislation, which seeks provisions to permanently prevent Iran from acquiring nuclear weapons and subject Iran's long-range missile program to severe sanctions.

The legislation is required to include certain "triggers" which will automatically lead to a reimposition of the sanctions if Iran fail to apply.

Trump is also seeking for a follow-on agreement with the European allies that will eliminate the "sunset" clauses in the current agreement, said senior Trump administration officials who briefed reporters on the decision on Friday afternoon.

"If at any time I judge that such an agreement is not within reach, I will withdraw from the deal immediately," said Trump in the statement.