United Nations Secretary-General Antonio Guterres warned on Thursday against scrapping an international deal on Iran's nuclear program unless there was a good alternative in place.
U.S. President Donald Trump has been threatening to pull out of the agreement, leading to diplomatic tensions with Iran as well as with U.S. allies keen to preserve the agreement.
"If one day there is a better agreement to replace it it's fine, but we should not scrap it unless we have a good alternative," Guterres said in an interview with BBC Radio 4.
"I believe the JCPOA (the Iran nuclear deal) was an important diplomatic victory and I think it will be important to preserve it but I also believe there are areas in which it will be very important to have a meaningful dialogue because I see the region in a very dangerous position," he said.
Li Guofu, a researcher at China Institute of International Studies, said there remains room for changes although it seems irreversible that the United States will withdraw from the Iran nuclear agreement.
Two officials from the White House and a source familiar with the administration's internal debate claimed on Wednesday that Trump has all but decided to withdraw from the 2015 Iran nuclear accord by May 12 but exactly how he will do so remains unclear.
"It's hard to predict Trump's behavior," said Li. "But all kinds of signs we can see indicates that he might want to withdraw from the deal if there is no big changes."
The arguments focus on completely destroying Iran's nuclear capability and stopping it from developing ballistic missiles, which Iran can hardly accept.
Li said the European leaders, on the contrary, think the deal is still working, and Germany, France and Britain decide to impose sanctions on Iran's ballistic missiles as long as the U.S. promises to stay within the framework.
The nuclear deal, officially known as the Joint Comprehensive Plan of Action, was reached in 2015 between Iran and a group of world power: China, the U.S., Britain, Russia, France and Germany, agreeing to limit Iran's nuclear activities in return for the lifting of crippling economic sanctions.
Under the deal, Iran is committed to slashing the number of its centrifuges and cut its stockpile of enriched uranium drastically and not enrich remaining uranium to the level needed to produce nuclear weapons.
Technically, Trump must decide by May 12 whether to renew "waivers" suspending some of the U.S. sanctions on Iran.
Trump has pilloried the agreement as "insane" and "ridiculous" and called for fresh measures to counter Iran's ballistic missile program.
A presentation by Israeli Prime Minister Benjamin Netanyahu on Monday showing what he said was documentary evidence of Tehran's past nuclear arms program could give Trump a fresh argument to withdraw. Fan Jishe, director of Institute of American Studies at Chinese Academy of Social Science, said it is possible for the U.S. to quit while there is also chance for Washington to postpone its deadline again to renew its support for the deal.
"Trump is constantly opposed to the deal and his administration don't like it either. Plus, there is not enough time to renegotiate and settle down the arguments before May 12, although Europe has been trying to solve part of the problem," he said.