Hawks often complain that Iran negotiates only to buy time to expand its nuclear capability, but Western leaders know that their economic choke hold on Iran will tighten regardless of what happens at the talks. An E.U. embargo on importing Iranian oil will take effect in two weeks’ time, as will new banking sanctions designed to cut Iran off from international trade and finance. Western powers haven’t put those measures up for negotiation, except in the highly unlikely eventuality that Iran suddenly capitulates on the issue at the heart of the standoff by stopping all enrichment of uranium in line with U.N. Security Council resolutions. Having defied that demand at great cost but with broad domestic support for six years, Iran insists that it has no intention of backing down on 3.5% enrichment. Indeed, one of its core demands for any movement on 20% enrichment has been for Western powers to acknowledge its right, under the Nuclear Non-Proliferation Treaty, to enrichment for peaceful purposes.

The Iranians appear to believe Western powers need a deal more than they do because of the potentially disastrous impact on the world economy of any confrontation over Iran. And they see the talks that began in Istanbul in the spring as a vindication of their defiance, believing Western powers will back down on low-level enrichment. But Western officials believe Iran has been forced to the table under the pain of sanctions, which gives the U.S. and its allies the whip hand. Regardless of the outcome of the Moscow talks, there will be a sharp escalation of pressure in the weeks ahead. Already, sanctions have cut Iran’s oil exports by as much as 40%, sent consumer price inflation soaring by 40% and halved the value of its currency, the rial.

In a reliably trenchant analysis, the International Crisis Group (ICG) sees a perilous situation emerging as a result of both sides’ overestimating their leverage. Western officials have operated on the assumption that sanctions and the threat of Israeli military action brought the Iranians to the table, but Tehran “also felt that it was in the driver’s seat, having strengthened its position over the preceding year by increasing its stockpile of low-enriched uranium, enriching at higher levels and completing its work on the underground nuclear facility at Fordow,” according to the ICG. Iran also knows that, in an election year, President Obama can’t risk the sort of economic shock that could be triggered by a confrontation.