On Tuesday, the US Treasury Department issued a statement announcing new sanctions targeting Taliban members involved in suicide attacks and other lethal offensives in Afghanistan, along with Iranians who have provided material and financial support to the militant group.

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Two Iranian nationals linked to the Quds Forces of Iran's Revolutionary Guard, two Pakistanis and four Afghans are among the newly sanctioned individuals, meaning the US government can now freeze any of their assets or property under American jurisdiction.

However, it is unlikely that the newly sanctioned individuals own assets in the US. And sanctions are only marginally effective in stopping the flow of Taliban financing because the insurgent group has many avenues of funding, for example, with the record-high opium harvests in Afghanistan.

A different perspective on sanctions is that they highlight US frustration with Iran's role in Afghanistan.

Both Kabul and Washington consider Pakistan to be the Taliban's main supporter, and the country is a known sanctuary for militants.

However, in recent years the Taliban have extended links to other countries, including Iran and Russia, in an attempt to expand regional backing.

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The group's former leader, Mullah Mansoor, was killed by a US drone strike in May 2016, shortly after returning to Pakistan from Iran.

"The US has enough to worry about with the support the Taliban derives from Pakistan," Michael Kugelman from the Washington-based Woodrow Wilson Center for Scholars said, adding the US does not want the Taliban to have a second external partner.

"But that's what seems to be evolving now as Iran often plays a double game in Afghanistan," Kugelman told DW. "Iran engages heavily with the government in Kabul, but at the same time it provides episodic levels of small arms support to the insurgents," he said.

How close are the Taliban to Iran?

As international pressure on Pakistan increases, the Taliban continue to look for other countries that could provide the support needed to ensure their existence, in case Islamabad turns away.

On the other hand, with the US-Iran relationship taking a nosedive under US President Donald Trump's administration, there's good reason to believe that the Iranians are increasing support for the Taliban and other groups that are fighting US forces in Afghanistan.

"The Quds Forces are a Taliban contact point with Iran, but their support to the insurgent group has so far remained secretive," Kabul-based military analyst Jawid Kohistani told DW.

"The Quds Forces have been able to launch operations in Syria and Iraq, and they are very well capable of doing the same in Afghanistan," he added.

A surge in Taliban activity in western Afghan provinces that share a border with Iran also points to potential cooperation between the Taliban and Iranian forces.

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According to Kugelman, the Taliban's recent offensive in western Farah province — near the border with Iran — could indicate that the group was receiving some degree of assistance from Iranian intelligence operatives across the border.

"We certainly have to assume that the Revolutionary Guard could be making covert forays into Afghanistan to provide some form of support to the insurgents," he said.

Read more: What is Iran's Revolutionary Guard?

US officials have been vocal about what they call Iran's "distractive role in Afghanistan." US Treasury Secretary Steven Mnuchin has accused Iran of providing military training, financing and weapons to the Taliban, warning that Washington will not tolerate Iran's destabilizing behavior in Afghanistan.

But former Afghan diplomat Ahmad Said believes it is just an exaggeration.

"The Taliban's main ally in the region is Pakistan, not Iran," he told DW. "The US should go after Pakistan if it wants to hurt the Taliban."

A new obstacle to Afghan peace?

The Taliban have demanded the removal of the group's leadership from the US sanctions list as a precondition for peace talks. 

Although new sanctions on the Taliban could hurt US efforts to start direct talks with the militant group, many experts say the sanctions have more of a symbolic impact than anything else.

Efforts toward peace talks are struggling due to the Taliban's utter lack of an incentive to stop fighting when they think they're winning the war.

Read more: US-Taliban talks could undermine Afghan government

"The sanctions issue won't make or break the possibility of peace talks," Kugelman stressed.

Washington recently appointed former Afghanistan ambassador Zalmai Khalilzad as the top US diplomat for Afghan peace talks. Khalilzad has already held talks with Afghan and Pakistani officials as well as Taliban members in Qatar.

Recent US efforts toward peace, Kohistani said, could only yield results if combined with pressuring the Taliban on the battlefield, cutting the group's finances and disrupting support from outside Afghanistan.

"In this context, I even think current and future sanctions could help the Afghan peace process," he said.