Former US secretary of state John Kerry.
By  GLOBE STAFF  
WASHINGTON — John Kerry’s bid to save one of his most significant accomplishments as secretary of state took him to New York on a Sunday afternoon two weeks ago, where, more than a year after he left office, he engaged in some unusual shadow diplomacy with a top-ranking Iranian official.
He sat down at the United Nations with Foreign Minister Javad Zarif to discuss ways of preserving the pact limiting Iran’s nuclear weapons program. It was the second time in about two months that the two had met to strategize over salvaging a deal they spent years negotiating during the Obama administration, according to a person briefed on the meetings.
With the Iran deal facing its gravest threat since it was signed in 2015, Kerry has been on an aggressive yet stealthy mission to preserve it, using his deep lists of contacts gleaned during his time as the top US diplomat to try to apply pressure on the Trump administration from the outside. President Trump, who has consistently criticized the pact and campaigned in 2016 on scuttling it, faces a May 12 deadline to decide whether to continue abiding by its terms.