Iran and United Nations have signed an agreement about providing humanitarian assistance in the Middle East, including to Syria, a semi-official Iranian news agency reported on Sunday.

The ISNA news agency quoted Deputy Foreign Minister Abbas Araghchi as saying that the agreement came after a meeting with UN humanitarian chief Valerie Amos. Amos is on her first visit to Tehran.

Araghchi said Iran is ready for extended and effective cooperation with the United Nations for humanitarian aid. He was quoted as saying: "There are plenty of crisis caused by political developments in the Middle East, like what we are currently witnessing in Syria."

The Iranian speaker of parliament earlier Sunday welcomed a U.S. decision to back down from an attack against Syria as a sign of "rationality," Iranian media reported on Sunday.

In a late-evening news conference, speaker Ali Larijani said that any U.S. strike in retaliation for the gas attack would result in a larger conflict in the region and would be against international law - and that U.S. policymakers had realized this.

"We are hopeful that American politicians have some rationality so they avoid extremist behavior, and the events of the last few days and the decisions that have been taken indicate this rationality," Larijani said, according to the ISNA news agency on Sunday.

Iran is key regional backer of Syrian President Bashar Assad in the country's civil war. It has occasionally sent humanitarian aid to Syria in the past.