Britain's top diplomat is visiting the United States for two days of talks with the Trump administration as President Donald Trump decides whether to pull out of the multinational nuclear agreement with Iran.

British Foreign Secretary Boris Johnson is a strong proponent of the deal. Trump has given Britain, France and Germany a May 12 deadline to fix what he views as the deal's flaws - its failure to address Iran's ballistic missile program, the terms by which inspectors visit suspect Iranian sites, and "sunset" clauses under which some of its terms expire - or he will reimpose US sanctions.

The agreement itself isn't cited as a discussion point in a statement on the trip from Britain's Foreign Office. But Iran is listed as one of the international issues Johnson is to discuss along with the Korean Peninsula and Syria.

The statement said Johnson was expected to meet with US Vice-President Mike Pence, National Security Adviser John Bolton and other senior administration officials as well as congressional foreign policy leaders.

Meanwhile, Israeli Prime Minister Benjamin Netanyahu said on Saturday that he was scheduled to meet Russian President Vladimir Putin on Wednesday in Moscow to discuss regional issues.

It will be the eighth meeting between the two leaders in the past two years, in addition to at least 12 phone talks, according to Israeli media.

Israel has been lobbying world powers to "fix or nix" the 2015 nuclear deal with Iran as a May 12 deadline set by Trump approaches.

Israel is also concerned that Iran is establishing a military presence in Syria, and it has attacked Iranian targets there.

On Thursday, Israel's defense minister reminded Russia of his government's decision not to join Western sanctions against it, and asked that Moscow reciprocate with a more pro-Israel approach over Syria and Iran issues.

Moscow has repeatedly said it wants the Iran nuclear deal left intact. Foreign Ministry spokeswoman Maria Zakharova said on Friday that Russia would deem any changes to the deal to be unacceptable.

On Sunday, Iranian President Hassan Rouhani said Teheran had prepared plans to respond to any decision by Trump to end the nuclear agreement and the Washington would regret such a decision.

"We have plans to resist any decision by Trump on the nuclear accord," Rouhani said in a speech carried live by state television. "If America leaves the nuclear accord, this will entail historic remorse for it."

Reuters, AP and Xinhua contributed to this story.