The United States on Tuesday lifted sanctions barriers on private groups that want to send relief funds to Iran in the wake of the August 11 earthquake disaster in the country's northwest.

The US Treasury said non-governmental organizations could transfer up to $300,000 to Iran for quake relief over the next 45 days without contravening Washington's tight ban on financial or business transactions with the country.

"Under the general license, which will remain in effect until October 5, 2012, an NGO can transfer funds up to $300,000 during the 45-day period to Iran to be used for humanitarian relief and reconstruction activities related to the earthquake response," the Treasury said.

"NGOs interested in transferring more than $300,000 during the 45-day period may apply for a specific license."

After the quake Washington said Americans could send food and medicine for relief, but ran into complaints that charity donations were blocked.

The National Iranian American Council applauded the Treasury's move Tuesday.

"This humanitarian gesture will empower the American people to help Iranians who've lost everything to this terrible natural disaster," said NIAC assistant policy director David Elliott.

"The onus is now on the Iranian government to put the well-being of its people first and eliminate all obstacles for delivering aid to the Iranian people," he said.

On August 15 Tehran rejected the US offer of food and medicine, blaming existing sanctions for shortages of both.

"We do not believe the US put forward the offer in good faith. We are currently having a medicine supply crisis because of sanctions," said Hassan Ghadami, the head of the interior ministry's crisis management organization.

The Treasury meanwhile warned that any financial aid that NGOs provide cannot pass through the hands of specific US-blacklisted Iranian groups such as the Revolutionary Guards.

"It is important to note that the general license specifically forbids any dealings or involvement with individuals or entities designated for support for the proliferation of weapons of mass destruction or terrorism," the Treasury said.