The four Arab states leading a boycott of Qatar said late Thursday that they would take all the necessary measures to stop the oil-rich Gulf state's support of extremism.
Saudi Arabia, the United Arab Emirates, Bahrain and Egypt said in a joint statement published on Emirati news agency WAM that it would "take all necessary political, economic and legal measures" against Qatar. The group said it would decide the new measures in a "timely manner" and would seek to "preserve the four countries' rights, security and stability."
It did not specify what the new actions against Qatar could be, and it stopped short of saying explicitly that it would resort to force. Tensions have continued to rise over the boycott, driven in part by Qatar's relationship with Iran, the Shia regional powerhouse that is battling Sunni-ruled Saudi Arabia's influence in the Middle East.
The four countries cut diplomatic and transport ties with Qatar on June 5 over its alleged support for extremist groups. In a list of 13 demands issued with a 10-day ultimatum to resolve the crisis, they accused Qatar of supporting the extreme vision of groups such as Al-Qaeda and the Islamic State militant group (ISIS). The list calls on Qatar to outlaw these groups, as well as Lebanese Shiite militant group Hezbollah and the Al-Qaeda affiliate once known as the Nusra Front.
But Qatar denies any support for extremist groups and believed the demands to be heavy-handed and unnecessary, ultimately rejecting them this week.
In the four countries' statement, they said Qatar's refusal "reflects its intention to continue its policy, aimed at destabilizing security in the region."
Qatar has hosted leading figures from Palestinian militant group Hamas's politburo. The country says that hosting the group is not an advocation of their message, but a political acceptance of different views with the aim of promoting dialogue.
The U.S. is a key ally of Qatar, with its largest air base in the region stationed in the country to allow jets to launch bombing raids on the Islamic State militant group (ISIS) in Iraq and Syria, and on Thursday U.S. Defense Secretary Jim Mattis reaffirmed the strategic partnership between the two countries amid the regional spat.
The U.S. State Department announced that Secretary of State Rex Tillerson will travel to Kuwait on July 10 to discuss the rift. Kuwait has tried to mediate the crisis so far with little success.
"We've become increasingly concerned that that dispute is at an impasse at this point," State Department spokeswoman Heather Nauert told reporters Thursday. "We believe that this could potentially drag on for weeks. It could drag on for months. It could possibly even intensify."
