The US and the EU's lifting of crippling sanctions on Iran was today welcomed as a "significant milestone" by the United Nations and world powers like Britain and China, who also termed the achievement as "hard-earned".
The implementation reflects the "good faith effort by all parties to fulfil their agreed commitments" UN Secretary- General Ban Ki-moon said in a statement, hours after Iranian Foreign Minister Javad Zarif along with EU foreign policy chief Federica Mogherini made the announcement in Vienna.
UK Foreign Secretary Philip Hammond said the nuclear deal with Iran, in which Britain played a major role, makes the Middle East and the wider world a safer place.
"Years of patient and persistent diplomacy, and difficult technical work, have borne fruit as we now implement the deal," he said.
China welcomed the landmark Iran nuclear deal reached in July last year as a "hard-earned" achievement and said the agreement leading to the lifting of sanctions against Tehran is "worth celebrating".
Chinese Foreign Minister Wang Yi said that the "Implementation Day" of the agreement was a solid step on the way to the final political and diplomatic settlement of the Iranian nuclear issue.
The international sanctions were lifted after the UN nuclear agency International Atomic Energy Agency (IAEA) announced that Tehran has met its obligations it committed under the deal agreed between world powers and Iran.
Ban welcomed the achievement of Implementation Day under the Joint Comprehensive Plan of Action (JCPOA) and commended the "dedication and determination" shown on all sides. He also encouraged the parties to continue to implement the JCPOA in the months and years ahead.
The Secretary-General voiced hope that "the success of this agreement contributes to greater regional and international cooperation for peace, security and stability in the region and beyond".
The UN stands ready to support the implementation of the JCPOA in accordance with the relevant decisions of the Security Council, Ban said, adding that this achievement demonstrates that international proliferation concerns are best addressed through dialogue and patient diplomacy.
US Ambassador to the UN Samantha Power said that "following the pressure brought to bear by the US and the international community, Iran has taken real, observable action that quadruples Iran's breakout time - a result that seemed improbable as recently as two years ago when negotiations on the JCPOA began".
However, Israel remained pessimistic about the deal as Prime Minister Benjamin Netanyahu accused Iran of still seeking nuclear military capabilities, destabilising the region and spreading terrorism globally.
"Israel will continue to monitor Iran's negative activities and will take all necessary measures to maintain its security and defend itself," the Prime Minister's Office said.