Qatar said Tuesday the demands of Arab rivals in a Gulf diplomatic crisis were impossible to meet, ahead of talks in Egypt between Saudi Arabia and allies that have cut ties with Doha.

Qatari Foreign Minister Sheikh Mohammed bin Abdulrahman Al-Thani told a press conference in Doha that the list of conditions for restoring relations "is unrealistic and is not actionable".

"It's not about terrorism, it's talking about shutting down the freedom of speech," he said at a joint press conference after talks with his German counterpart Sigmar Gabriel.

Saudi Arabia, the United Arab Emirates, Bahrain and Egypt -- who accuse Qatar of supporting extremism -- gave Doha an extra 48 hours to meet their demands after an initial 10-day deadline expired on Sunday.

The demands included Doha ending support for the Muslim Brotherhood, closing broadcaster Al-Jazeera, downgrading diplomatic ties with Iran and shutting down a Turkish military base in the emirate.

Sheikh Mohammed handed an official response on Monday to Kuwait, which is mediating in the dispute, but its contents have not been disclosed.

He refused Tuesday to give any further details, but said Doha was looking for a solution to the month-long crisis based on dialogue.

"The state of Qatar has adopted a very constructive attitude since the beginning of the crisis. We are trying to act mature and discuss the matter," he said.

On Tuesday Qatari Emir Sheikh Tamim bin Hamad Al-Thani received a written response from Kuwait's Emir Sheikh Sabah al-Ahmad Al-Sabah, the official Qatar News Agency reported, without elaborating.

The four countries cut diplomatic and transport links with Qatar a month ago and have suggested further sanctions could be imposed if Doha does not comply.

Foreign ministers from Saudi Arabia, the United Arab Emirates, Bahrain and Egypt are to meet in Cairo on Wednesday to discuss the diplomatic crisis, the worst to hit the region in years.

Qatar, which denies any support for extremists, has said it will not bow to pressure and that the demands seem designed to be rejected.

The UAE has accused Doha of supporting Al-Qaeda-linked groups in Syria, Libya and Yemen.

Qatar is the world's leading producer of Liquefied Natural Gas (LNG) and on Tuesday the head of state-owned Qatar Petroleum said it was planning a significant production increase over the coming years.

Saad Sherida Al-Kaabi told a press conference that the emirate intends to produce 100 million tonnes of natural gas a year by 2024, up 30 percent from current levels.

"This new project will strengthen Qatar's leading position," Kaabi said. "We will remain the leader of LNG for a very long time."

- 'Absolutely no fear' -

Some officials have suggested if Qatar does not cooperate, Riyadh and its allies could tell foreign companies to choose between doing business with them or with Doha.

Kaabi said Qatar wanted the gas production increase to be carried out through a joint venture with international companies but that Doha could go it alone if necessary.

"We have absolutely no fear of having the embargo in place," he said. "If there are no companies willing to work with us we will go to 100 million (tonnes), 100 percent."

Riyadh and its allies have also accused Doha of being too close to their regional arch-rival Iran, which shares an enormous gas field with Qatar in the Gulf.

The crisis has raised concerns of growing instability in the region, home to some of the world's largest energy exporters and key Western allies who host US military bases.

Qatar's gas riches have transformed it into one of the world's wealthiest countries, a major international investor and a regional player that will host the 2022 football World Cup.

Qatar has also pursued a more independent foreign policy than many of its neighbours, who tend to follow the lead of regional powerhouse Saudi Arabia.

UAE Foreign Minister Sheikh Abdullah bin Zayed al-Nahyan said Tuesday it was "premature" to discuss what further action might be taken against Qatar.

Any measures that are taken will be "within the framework of international law," he said.

"Any independent state has the right to take measures against any party," Sheikh Abdullah said, urging Doha to listen to "the voice of reason and wisdom."