The United States is still refusing to accept certain clauses of a potential memorandum of understanding (MoU) with Iran on ending the war, the semi-official Tasnim news agency reported on Sunday.

Citing information obtained by its reporter, Tasnim said that despite some talks held between the two sides on Sunday, the United States is still obstructing certain clauses of the potential peace MoU, including the release of Iran's frozen assets.

It added that there is still a possibility that the MoU would be canceled, and Iran has stressed that it will not back down from its red lines in safeguarding the rights of its people.

On Saturday, Iranian Foreign Ministry spokesman Esmaeil Baghaei told state-run IRIB TV that Iran and the United States are working to finalize an MoU on ending the war.

"At this stage, our focus is on ending the imposed war," Baghaei stressed, adding, "Our intention has been to firstly agree on an MoU consisting of 14 clauses."

He noted that "within a period of 30 to 60 days," Tehran and Washington would reach a final agreement, saying, "Among the major topics to be addressed in the MoU are the cessation of U.S. maritime attacks, or naval blockade as they themselves call it, and other issues pertaining to the release of Iranian frozen assets."

Iran, the United States and Israel reached a ceasefire on April 8 after 40 days of fighting that started with U.S. and Israeli attacks on Iran on Feb. 28.

Following the truce, Iranian and U.S. delegations held one round of peace talks in Pakistan's Islamabad on April 11 and 12, which failed to yield an agreement.