The comments on Tuesday by Sheikh Mohammed bin Abdulrahman Al Thani came after a meeting with his US counterpart, Rex Tillerson, in Washington, DC, and followed an earlier statement by the Saudi foreign minister who said that there will be no negotiations over his country's demand that Qatar stops supporting "terrorism" - an allegation Doha strongly denies.
"What has been presented by the countries of the blockade are merely claims that are not proved by evidence and are not demands," said Sheikh Mohammed bin Abdulrahman Al Thani. "Negotiations require a real will by the other party and evidence to support its demands."
He added: "The demands must be realistic and enforceable. Anything else is rejected ... We agree with Washington that the demands should be rational."
The US, which urges a diplomatic solution to the crisis, has been pushing for a clear list of grievances that are "reasonable and actionable".
Al Jazeera's James Bays, reporting from Washington, DC, said that the Qatari government's position that these demands could not be met by Doha was, in a way, also backed by Heather Nauert, the US state departent spokesperson, who told reporters that "some of them will be difficult for Qatar to incorporate and to try to adhere to".
Saudi Arabia, the United Arab Emirates (UAE), Bahrain and Egypt cut diplomatic ties with Qatar and imposed sanctions on the country on June 5, accusing it of supporting "terrorism".
The four Arab countries have not provided any evidence for their claim, while Qatar has repeatedly rejected the allegation.
After more than two weeks, the Saudi-led bloc issued a 13-point demand list late on Thursday in exchange for the end of the anti-Qatar measures and gave a 10-day deadline.
The demands included, among others, that Qatar shut down the Al Jazeera media network, close a Turkish military base and scale down ties with Iran.
In the 13-point list, the countries also demand that Doha sever all alleged ties with the Muslim Brotherhood and other groups, including Hezbollah, al-Qaeda and ISIL, and pay an unspecified sum in compensation for what they claimed to be "loss of life and other financial losses caused by Qatar's policies".
Commenting on the list of demands, Tillerson on Sunday said some of the demands "will be very difficult for Qatar to meet". Nevertheless, he added that the list includes "significant areas which provide a basis for ongoing dialogue leading to a resolution".
Turkish President Recep Tayyip Erdogan has denounced the demands as being "against international law", while Sigmar Gabriel, Germany's foreign minister, has called them "very provocative".
Source: Al Jazeera and news agencies