Saudi-led bloc dismiss Kuwaiti emir's remarks on Gulf crisis
Saudi Arabia, Bahrain, UAE and Egypt said they "regret" several comments made by Sheikh Sabah, who on Thursday said he was hopeful that a resolution to the crisis could be reached.
The quartet said "any dialogue on meeting their demands should not be preceded by any prior conditions".
Sheikh Sabah's remarks, which came on Thursday during a White House news conference with US President Donald Trump, noted that Qatar had been presented with a list of 13 demands by the other countries and was willing to discuss them.
Although Qatar has rejected some of them out of hand, Sheikh Sabah said he believed negotiations were possible.
"I am optimistic that the solution will come in the very near future," he said. "The hope has not ended yet."
The 88-year-old Kuwaiti emir's efforts to resolve the diplomatic dispute were hailed by the US President Donald Trump.
Trump seeks to mediate personally
Trump applauded Kuwait's "critical contributions to regional stability" but also repeated an offer to mediate himself, particularly between Qatar and Saudi Arabia and the UAE.
He suggested a deal would be "worked out very quickly" if he became personally involved.
Trump said all the countries involved - members of the Gulf Cooperation Council - are "essential partners" with the United States in efforts to crack down on extremism, including the fight against the Islamic State group.
"We will be most successful with a united GCC," Trump said.
"We will send a strong message to both terrorist organisations and regional aggressors that they cannot win."
His comments came after he sent conflicting signals about where he stands on the dispute.
Trump initially appeared to side with Saudi Arabia, but then instructed Secretary of State Rex Tillerson to support the Kuwaiti mediation effort.
Qatar Emir to meet Germany's Angela Merkel
Meanwhile, Qatari Emir Sheikh Tamim bin Hamad Al-Thani is expected to visit Germany and meet with Chancellor Angela Merkel for talks on September 15.
The trip will be his first to a western capital since his country was blockaded by the neighbouring states.
The talks are expected to be dominated by the fate of Qatar amid the blockade.
The recent Gulf crisis began in June 5 when Saudi Arabia, Bahrain, Egypt, and the UAE all cut ties to Doha over allegations that Qatar funds extremists and has ties that are too warm with Iran.
The blockading states shut down air, maritime and land links with Qatar, and imposed economic sanctions the gas-rich emirate.
Qatar, which hosts a US military base critical to the effort to defeat IS in Iraq and Syria, has long denied funding extremists.
Agencies contributed to this report.