Saudi Arabia and three other Arab states have extended the deadline for Qatar to accept a list of demands by 48 hours, or face further sanctions.
The initial deadline for Qatar to agree to the group’s 13 demands, including the shutting down of the Al Jazeera news network, expired on Sunday.
The Gulf state, which denies funding extremism, has given a formal response, but details have not been released.
It has already called the demands an “affront to international law”.
The requirements include the closure of a Turkish military base in Qatar and the curbing of diplomatic relations with Iran.
Qatari Foreign Minister Sheikh Mohammed bin Abdul Rahman al-Thani was in Kuwait on Monday to hand over a formal response in the form of a letter from the emir of Qatar to the emir of Kuwait, the main mediator in the Gulf crisis.
In a statement released shortly beforehand, lawyers for Qatar denounced the demands and called for international condemnation.
They said the tactics were “reminiscent of the extreme and punitive conduct of ‘bully’ states that have historically resulted in war.
“The world must unite immediately to halt the singling out of Qatar for unjustified collective punishment and humiliation and to preserve peace, security and prosperity in the region.”
Qatar has been under unprecedented diplomatic and economic sanctions for weeks from Saudi Arabia and its allies, Egypt, the United Arab Emirates (UAE) and Bahrain.
The four countries, whose foreign ministers will meet on Wednesday to discuss the situation, have accused Qatar of harbouring Islamist groups that they consider terrorist organisations – including the Muslim Brotherhood – and giving them a platform on the Al Jazeera satellite channel, which is funded by the Qatari state. Doha denies the accusations.
The imposed restrictions have caused turmoil in Qatar, an oil- and gas-rich nation dependent on imports to meet the basic needs of its population of 2.7 million. As a result, Iran and Turkey have been increasingly supplying it with food and other goods.