Qatar is ready to discuss "legitimate issues" with Arab states to end a regional crisis, but it said a list presented by them last week contained some demands that were impossible to be met because they were not true.

The feud erupted this month when Saudi Arabia, the United Arab Emirates, Bahrain and Egypt broke off ties with Qatar, accusing it of supporting terrorism and being an ally of regional foe Iran. Severing diplomatic and travel links set off one of the worst rifts in years between the US allies.

The four countries have sent Doha a list of 13 demands, including closing the state-funded Al Jazeera television and reducing ties to Iran, an official of one of the four countries said, and gave Doha 10 days to comply.

The deadline is expected to expire on Sunday.

Qatari Foreign Minister Sheikh Mohammed bin Abdulrahman al-Thani said on Thursday that Doha was interested in negotiating legitimate issues concerning fellow Gulf states, but said some of the demands were not reasonable.

"We cannot 'sever links with so-called Islamic State, al-Qaeda and Lebanese Shia militant group Hezbollah' because no such links exist," he said in a statement. "And we cannot 'expel any members of Iran’s Revolutionary Guard' because there are none in Qatar."

The UAE ambassador to Russia has said Qatar could face fresh sanctions if it does not comply with the demands. The Gulf states could ask their trading partners to choose between working with them or Doha, he said in a newspaper interview.

Sheikh Mohammed said that since it was impossible for Doha to stop doing things it had never been doing, "we are left to conclude that the purpose of the ultimatum was not to address the issues listed, but to pressure Qatar to surrender its sovereignty. This is something we will not do".

Nato ally Turkey has backed Doha in the rift with four Arab states. Qatar's defence minister is due to visit Ankara on Friday and will hold talks with his Turkish counterpart, sources at Turkey's defence ministry said on Thursday.

Kuwait, which retained ties with Qatar, is trying to mediate in the dispute with the support of Washington.

UAE Minister of State for Foreign Affairs Anwar Gargash urged Qatar to choose its Arab neighbours.

"As the hour of truth approaches, we call on the brother to choose his neighbours, choose honesty, truth and transparency in its dealings and to realise that the noise of the media and the heroism of ideology are just a passing illusion," he said in a message on his Twitter on Wednesday.

UAE Prime Minister and Dubai ruler Sheikh Mohammed bin Rashid al-Maktoum published a poem on his Instagram account overnight on Wednesday in which called on "brother" Qatar to unite with the rest of the six-nation Gulf Cooperation Council.