The list of demands delivered to Qatar from Saudi Arabia last week would be "very difficult for Qatar to meet," U.S. Secretary of State Rex Tillerson said in a statement Sunday.

Tillerson added that there were still, "significant areas which provide a basis for ongoing dialogue leading to resolution," while calling on all parties to seek unity in the fight against terror.

Four Gulf Arab states presented Qatar with a list of 13 demands Friday, including calls to close the Turkish base in the country, to shut down the Al Jazeera TV channel and to cut off ties with Iran.

Qatar officials have dismissed the list as unrealistic and unfair. "This list of demands confirms what Qatar has said from the beginning – the illegal blockade has nothing to do with combating terrorism, it is about limiting Qatar's sovereignty," Qatari spokesperson Sheikh Saif bin Ahmed Al Thani said in a statement Friday.

Regional allies have also come out in opposition to the list of demands. Turkish President Recep Tayyip Erdoğan said, "we consider the 13-point list against international law."

Additionally, in a readout of a conversation with Qatar's emir, Iranian president Hassan Rouhani said, "pressure, threats and sanctions" would not assist in resolving the crisis, adding that the "siege of Qatar is not acceptable for us."

Four gulf states, led by Saudi Arabia, severed ties with Qatar on June 5 over accusations that the country was destabilizing the Middle East and funding extremism. Since then the four nations have placed an embargo on all traffic to the country.