Saudi Arabia, the United Arab Emirates, Egypt, and Bahrain released a joint statement carried by the countries' state media saying their initial list of 13 demands was now void.
The four Arab states leading the boycott against Qatar said late on Thursday that Doha's refusal of their demands to resolve a Gulf diplomatic crisis is proof of its links to terror groups and that they would enact new measures against it.
Saudi Arabia, the United Arab Emirates, Egypt, and Bahrain released a joint statement carried by the countries' state media saying their initial list of 13 demands was now void and pledging new political, economic and legal steps against Qatar.
The Qatari government sabotaged diplomatic efforts to solve the rift, the four states said, and its refusal affirmed its continuing sabotage of the region's stability and security.
Any measures taken by the four states would be aimed at the Qatari government but not its people, they said, without elaborating on when the new steps would be announced or what they would entail.
Foreign ministers from the four states convened in Cairo the day before after the expiry of a 10-day deadline for their demands to be met. They condemned Qatar's response as "negative" and lacking in content.
Since last month, the countries have cut diplomatic and transport ties with Qatar, which they accuse of supporting terrorism and allying with regional foe Iran. Doha denies the charges.
Among their demands were orders for Qatar to curtail its support for the Muslim Brotherhood, shut down the Al Jazeera TV channel, close a Turkish military base in Doha and downgrade its ties with Iran.
US says dispute could intensify
The rift opened days after US President Donald Trump met Arab leaders in Riyadh in May and called for unity against Iran and militant groups. And now the US fears that the impasse and could drag on for a long time or intensify, the US State Department said on Thursday.
Underscoring US concerns about the crisis involving key allies in the Middle East, the department said Secretary of State Rex Tillerson plans to visit Kuwait, which is mediating in the dispute, on Monday.
In the latest top-level US contact with officials of the countries involved in the dispute, Defense Secretary Jim Mattis discussed the importance of easing tensions in a phone call with Qatari Minister of State for Defense Affairs Khalid Al Attiyah on Thursday.
"We remain very concerned about that ongoing situation between Qatar and GCC (Gulf Cooperation Council) countries," State Department spokeswoman Heather Nauert told a briefing.
"We've become increasingly concerned that that dispute is at an impasse at this point. We believe that this could potentially drag on for weeks. It could drag on for months. It could possibly even intensify," she said.
Mattis discussed the state of relations among Gulf Arab states and "the importance of de-escalating tensions" in his call with Attiyah, the Pentagon said in a statement.
The two officials "affirmed the strategic security partnership" of their countries and Mattis emphasised the importance of Qatar's contributions to the US-led coalition fighting Daesh, it added.
Qatar hosts the largest US Air Force base in the region. Saudi Arabia has been a close US ally for decades, and US President Donald Trump sealed a $110 billion arms deal with the kingdom during a visit in May.