Financial sanctions against Iran hit the country’s economy hard, forcing Tehran to negotiate rolling back its nuclear program with the West. But they’ve also kept Iranians from buying medicine, paying tuition for students studying abroad, and making other purchases — all activities still allowed.

The trouble is skittish banks. Many financial institutions are so worried about running afoul of U.S. sanctions and incurring huge fines that they’re unwilling to do any business with Iranians.

Advocates in the United States are pushing for a special “financial channel” between the United States and Iran that would facilitate approved deals for medical equipment, food, and cell phones. Now they want negotiators to include the proposal in any broader nuclear deal that the United States and its allies strike with Iran ahead of the Monday, Nov. 24, deadline.

“Many Iranian Americans have family and friends in Iran and are in need of a financial channel to engage in authorized transactions,” the National Iranian American Council (NIAC) stated in a recent letter to Barack Obama’s administration. “A direct financial channel would help facilitate legitimate transactions and would also boost the role Iranian Americans can play bridging the divide between the two countries.”

A direct link between a U.S. bank and an Iranian bank could also facilitate a broad array of commercial transactions if the Obama administration further loosens sanctions in return for Iran’s dismantling of its nuclear program.

But the plan’s prospects are diminishing as the clock ticks down for talks to conclude between Iran and its six negotiating partners: the United States, Britain, Russia, China, France, and Germany.

“In some ways, it is a do-or-die moment for the idea,” said Tyler Cullis, a policy associate at the NIAC. If a broader agreement is not reached, it’s unlikely that a humanitarian financial channel will come to fruition either, Cullis added.

American and Iranian negotiators are meeting in Vienna in hopes of hammering out a last-minute deal.* But with no sign yet of success, and with officials lowering expectations, it’s starting to look like another extension is coming.

“I’m not optimistic that we can get everything done by Monday,” British Foreign Secretary Philip Hammond said Wednesday, according to Reuters.

“But I think if we make some significant movement, we may be able to find a way of extending the deadline to allow us to get to the final deal if we’re making a good progress in the right direction.”

An extension could leave the status quo interim deal struck a year ago in place while officials try to nail down the details of a new plan. Under that arrangement, U.S. companies can route their legal Iranian transactions through approved European or Asian banks. But because those channels don’t connect directly with the United States, it’s unclear how much they’ve encouraged unsanctioned trade.

“I don’t know how much it’s being used, but I know I don’t have any clients using it,” said trade lawyer Doug Jacobson, who is based in Washington, D.C.

“The larger companies who have pre-existing banking relationships with European banks who will handle these types of transactions, that’s the preferred mechanism, rather than having to go through this channel, which ends up being very bureaucratic,” Jacobson added.

Many observers see the lack of exempt activities as a second-order problem with the real goal being getting a broad nuclear deal. If the two countries can’t agree on the degree of nuclear disarmament and sanctions relief, creating a financial channel to facilitate greater trade is a nonstarter.

“It’s an interesting idea with potential problems and potential benefits, but fundamentally it’s a tactical fix to a tactical problem,” said Zachary Goldman, a former Treasury Department sanctions official and head of New York University’s Center on Law and Security.