Secretary of State Rex Tillerson on Sunday criticized some of the demands by Saudi Arabia and its allies on Qatar as "very difficult" to meet and urged the countries to tamp down the rhetoric and start negotiating.
"Qatar has begun its careful review and consideration of a series of requests presented by Bahrain, Egypt, Saudi Arabia and UAE", said Tillerson.
Saudi Arabia, Bahrain, the United Arab Emirates and Egypt want Qatar to meet their 13-point ultimatum - ostensibly aimed at fighting extremism and terrorism - in return for an end to a almost three-week-old diplomatic and trade "blockade" of the emirate.
He called on the Arab countries to "sit together" with Qatar to work through what he hoped would be "reasonable and actionable" demands.
The demands include downgrading ties with Iran, a regional rival of Saudi Arabia; stopping support for Islamist groups; closing a Turkish military base in Qatar; and shutting down the Doha-based television broadcaster Al Jazeera and its channels.
However, the Arab states involved in the crisis are all close allies of the U.S., while the largest USA base in the Middle East is in Qatar.
Last week, before the anti-Qatar demands became public, State Department spokeswoman Heather Nauert was unusually blunt in criticizing the group of nations isolating Qatar and effectively dared them to come up with a list of Qatari misdeeds.
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The blockade of Qatar is "unacceptable" and Tehran's policy is to strengthen ties with Doha, Iran's state-run Islamic Republic News Agency cited President Hassan Rouhani as saying on Sunday.
Qatar's Foreign Ministry said it was "studying" the list, "in order to prepare an appropriate response".
"Here we see an attack against a state's sovereignty rights", Erdogan said.
On June 23, Turkish Defense Minister Fikri Isik had told a local broadcaster that the base in Qatar supports the security and stability of Gulf countries, and any call to shut the base acts as interference in Turkey's ties with Qatar. "Their role should be to put pressure on Qatar", said Gargash. The GCC, or Gulf Cooperation Council, includes Saudi Arabia, the UAE, Bahrain and Kuwait as well as Qatar.
The US maintains its largest concentration of military personnel in the Middle East at Qatar's Al Udeid Air Base.
The United Arab Emirates has been trying to mediate in the crisis.
"If Qatar does not respond to the demands, the alternative is not escalation, but parting", Gargash said at a televised press conference in Dubai.