A Saudi-led bloc of countries hostile to Qatar on Friday challenged statements by the Kuwaiti emir, denying his mediation has seen progress in finding a solution to the Gulf dispute.

Saudi Arabia as well as the United Arab Emirates, Egypt and Bahrain cut ties with Qatar in June, accusing it of bankrolling Islamist extremist groups.

Qatar, a gas-rich Gulf emirate, denies the claims and accuses the four countries of an attack on its sovereignty.

In Washington on Thursday, Kuwaiti Emir Sheikh Sabah al-Ahmad Al-Sabah gave an upbeat assessment of his mediation efforts during a joint news conference with US President Donald Trump.

In a statement early Friday, the Saudi-led bloc questioned the emir's statement that Qatar would be willing to accept their 13 demands.

"Dialogue on the implementation of the demands should not be preceded by any conditions," they said in the joint statement carried by the state-run Saudi Press Agency.

They also voiced "regret" about the Kuwaiti ruler's statement "on the success of mediation in stopping military intervention".

Instead, the four Arab states stressed in their joint statement that "the military option has not been and will not be considered in any case."

During Thursday's news conference, Trump offered to mediate in the crisis, saying he believed the dispute could be solved "fairly easily".

Riyadh and Doha are both key allies of the United States. Trump chose Saudi Arabia for his first overseas visit as president in May, two weeks before the Gulf crisis erupted.

Qatar is meanwhile home to a huge US air base, where the headquarters of Centcom -- the regional command which leads operations against the Islamic State jihadist group -- is based.