Obstacles to ending the decades-long enmity between Iran and the United States are so forbidding that even keeping talks going towards some sort of a deal would count as positive.
But as the Western allies and Russia resume talks today with the Iranians, Israel and sections of the United States Congress are laying more hurdles in the path.
Even France, a member of the Western conclave, appears to be wavering after an early burst of enthusiasm. No matter, such skirmishing is predictable in a process of such historical import. It is wise to not underestimate the negative influences on the talks, but focus should be fixed on the big prize.
Not since the emergence of Ayatollah Khomeini that altered the strategic look and tenor of West Asia have Iran and America come this close to a meeting of minds. This is largely due to President Barack Obama's belief in avoiding confrontation with the Islamic ummah if rapprochement is possible. If he can swing this deal, he will have earned the Nobel Peace Prize he had been presented with.
On the Iranian side, Mr Mohammad Khatami, an erudite observer of historical trends, tried to get a "dialogue of the civilisations" going when he was president, but got nowhere. This time the new President, Mr Hassan Rouhani, has been cleared by the apex leadership to talk with the Americans - but he is being held to a greatly circumscribed brief.
So complex and changing is the calculus that failure seems a more probable outcome.
An absence of trust lies at the heart of the matter. The US is suspicious of Iran's assertions that its nuclear programme is intended for peaceful purposes. Mr Rouhani's "red lines" on the right to enrich uranium represent in these circumstances red flags to the West, rightly or wrongly.
The Iranians conversely have reason to doubt Western sincerity. If they complied with demands to reduce nuclear works to a level accepted as non-lethal in application, can they be assured of reciprocity in removal of sanctions? Oil exports and the value of its currency are halved, unemployment and inflation are at ruinous levels. Iran is hurting.
Then there is the fear of Israel and Saudi Arabia that a rehabilitated Iran would diminish their clout in West Asia. One regards national security as sacrosanct while the other is intent on retaining influence in the Sunni-Shi'ite schism still playing out more than a thousand years later.
The Russians want to preserve their strategic hold through ties with Iran and other plans to revive the glory that was Russia.
But return to first principles the interlocutors must. If they can meet one another halfway on divergent interests, it would be accomplishment enough. At least they are talking, not plotting.
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