A few hours after the countries calling for combating terrorism accused Qatar of thwarting Kuwait’s efforts to solve the worsening crisis between the four states and Doha, the United States and Britain began new efforts to urge all parties to support Kuwaiti mediation efforts.

Qatar reiterated its rejection on Friday to the accusations of the four countries of supporting and financing terrorism and said they are “baseless.”

London and Washington have replaced phone conversations with face-to-face meetings with representatives of the four anti-terrorism countries (Saudi Arabia, UAE, Bahrain and Egypt) and participated with them in promoting Kuwait’s endeavors.

British Foreign Secretary Boris Johnson arrived Friday in Jeddah to discuss a solution to the crisis, maintaining the unity of Gulf states and facing common threats, represented in extremism and terrorism.

Meanwhile, US Secretary of State Rex Tillerson is heading to Kuwait on Monday following an invitation by Emir Sheikh Sabah al-Ahmad al-Sabah to discuss the issue.

Saudi Arabia, the UAE, Egypt and Bahrain have earlier accused the Qatari government of supporting and harboring terrorism and decided to cut diplomatic relations with it. The four countries later submitted 13 demands to be implemented as a condition for the return of relations, yet Doha’s response was negative.

In a joint statement on Thursday, the four countries said that Doha’s refusal to accept their demands to end the diplomatic standoff was proof of its links to terrorist groups.

In their statement, the four said the initial list of demands was now void and they pledged further political, economic and legal steps against the emirate.

Johnson will talk with Sheikh Mohammed bin Zayed, Crown Prince of Abu Dhabi and Deputy Supreme Commander of the Armed Forces, and Saudi Crown Prince Mohammed bin Salman, as well as representatives from Qatar and Kuwait at a currently undisclosed date.

“The Foreign Secretary will urge all parties to get behind Kuwait’s mediation efforts, which the UK strongly supports, and work towards deescalation and Gulf unity for the sake of regional stability,” the British foreign office said in a statement.

“He will also discuss a range of security and bilateral issues with a particular focus on working together to address the common threats of extremism, radicalization and terrorism.”

In a common matter, a US state department spokeswoman said Washington was growing “increasingly concerned that the dispute is at an impasse” and could drag on for months.

Underscoring US concerns about a crisis involving key allies in the Middle East, the department said Tillerson plans to visit Kuwait, which is mediating in the dispute, on Monday and will meet a number of senior Kuwaiti officials to discuss current efforts to solve the crisis.