DUBAI, United Arab Emirates - The United States' top diplomat concluded a week of shuttle diplomacy in the Persian Gulf crisis on Thursday, bearing no promise of a breakthrough but voicing optimism that Qatar and its four Arab neighbors might soon at least be willing to talk face to face.

US Secretary of State Rex Tillerson traveled to Qatar for a second time for a lunch meeting with 37-year-old Emir Tamim bin Hamad Al Thani, following talks earlier in the week in Kuwait and Saudi Arabia. As he flew back to Washington, Tillerson told reporters that the discussions had been "helpful" and that the US planned to keep at it.

"In my view, there's a changed sense of willingness to at least be open to talking to one another, and that was not the case before I came," Tillerson said.

It was a far cry from a US-brokered resolution to the crisis that has now spanned more than a month, and no meeting of the feuding nations has yet been announced. But Tillerson's aides had said ahead of time they didn't expect a quick solution from his four-day trip.

Tillerson, a former Exxon Mobil CEO with deep experience in the oil-rich Gulf, has been shuttling between Qatar, Saudi Arabia and mediator Kuwait since Monday trying to repair a rift that is dividing some of Washington's most important Middle East allies. Ahead of the trip, the US said the crisis was at an "impasse", but on Thursday the State Department said that was no longer the case.

Tillerson's clearest achievement was to secure a memorandum of understanding with Qatar to strengthen its counterterrorism efforts and address shortfalls in policing terrorism funding. That deal goes to the core of the quartet's complaints against Doha: that it provides support for extremist groups.

Qatar vehemently denies the allegation.

Saudi Arabia, Bahrain, Egypt and the United Arab Emirates said that the pressure and demands it had placed on Qatar helped lead to the counterterrorism pact, but it said the agreement does not go far enough to end the dispute.

The UAE Minister of State for Foreign Affairs said on Friday that there will be no quick end to the row.

"We are headed for a long estrangement ... we are very far from a political solution involving a change in Qatar's course, and in light of that nothing will change and we have to look for a different format of relations," Anwar al-Gargash said.

Ap - Reuters