US Secretary of State Mike Pompeo said a united Gulf region was essential for building a planned security and economic alliance of Middle Eastern states as he arrived in Qatar.
After meeting his Qatari counterpart, Sheikh Mohammed bin Abdulrahman Al Thani, Mr Pompeo flew to Saudi Arabia as he pushes on with his multi-leg Middle Eastern tour to reassure allies about Washington's commitment to the region.
He was greeted on the tarmac by Minister of State for Foreign Affairs Adel Al Jubeir and Saudi Ambassador to the US Prince Khalid bin Salman.
From Qatar he said that the crisis had gone on too long and said that the region faced challenges that required a unified stance.
"When we have a common challenge, disputes between countries with shared objectives are never helpful," Mr Pompeo, said from Doha.
"They never permit you to have as robust response to common adversaries or common challenges as you might," he added. "We're hoping that the unity of GCC will increase in the days and weeks and months ahead."
Saudi Arabia, the UAE, Bahrain and Egypt cut ties with Qatar in June 2017 saying its support for terror groups was a destabilising threat and said the country’s policies interfered in the internal affairs of its neighbours. The quartet has issued a list of demands they say Doha must compromise on before they will restore links.
Pompeo later told reporters that he had brought up the rift with officials in Bahrain, Egypt and the UAE. "It's ... not at all clear that the rift is any closer to being resolved today than it was yesterday and I regret that," he said.
The UAE and Saudi Arabia have said that the situation is not a priority and could maintain for the foreseeable future unless Qatar is serious about change but stated that it does not compromise defence cooperation with the US.
Mr Pompeo said that Gulf unity was essential for the planned Middle East Strategic Alliance – dubbed MESA – that would also include Jordan and Egypt.
America has proposed a nine-country alliance for security, economic and political cooperation. MESA has been dubbed an Arab Nato.
Mr Pompeo also said he had signed an agreement with Doha to expand the Al Udeid Air Base that operates as a forward position for America's Central Command and is home to some 10,000 US troops.
He is also set to raise the importance of peace in Afghanistan and countering Iranian policies in the Middle East.
The Taliban have a political office in Doha and Saudi Arabia and the UAE have played an important recent role behind the scenes in holding peace talks between the US and the armed Afghan group.
However, it is unclear where Qatar will stand on the issue of the US’s increasingly active policy against Iran given that it has strong links with Tehran.
Mr Pompeo is later expected to head to Riyadh, where all eyes will be on a possible meeting with Crown Prince Mohammed bin Salman.
Touching on the killing of Saudi journalist and critic of government policy, Jamal Khashoggi, in the kingdom’s embassy last year, Mr Pompeo said he would speak with the crown prince to ensure there is "full and complete" accountability.
A group of senior officials and security personnel were arrested for carrying out the killing which the Saudi government says the country’s leadership were unaware of. The trial of the 11 men opened at the start of the year.
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Meanwhile, Iranian Foreign Minister Mohammad Javad Zarif met with his Iraqi counterpart in Baghdad just days after Mr Pompeo’s surprise visit to the country.
After a two-hour meeting on Sunday, Iraq's top diplomat Mohammed Ali al-Hakim said he had talked through the restrictions with his counterpart.
"We discussed the unilateral economic measures taken by the US and are working with our neighbour (Iran) on them," Hakim said.
He said the two talked through various political and economic issues, including Syria and Yemen, in a "long and interesting meeting".
Tehran has also summoned Poland's ambassador and cancelled a Polish film festival over news that Warsaw would host a global summit to address the threat posed by the Iranian regime.
The Polish capital will be where dozens of countries are to gather at a February 13-14 meeting to “focus on Middle East stability and peace and freedom and security here in this region,” Mr Pompeo said on Friday.
America's top diplomat departed from Abu Dhabi after meeting with UAE ambassador to the US Yousef Al Otaiba. On Saturday evening, he met with Crown Prince and Deputy Supreme Commander of the UAE Armed Forces Sheikh Mohamed Bin Zayed. The pair discussed areas of cooperation and mutual interest between Washington and Abu Dhabi.
The meeting was attended by Khaldoon Al Mubarak, chief executive and managing director of Mubadala, chairman of the Abu Dhabi Executive Affairs Authority and Abu Dhabi Executive Council Member, Dr Anwar Gargash, UAE Minister of State for Foreign Affairs, Sheikh Abdullah bin Zayed, Minister of Foreign Affairs and International Co-operation, and Sheikh Tahnoon bin Zayed, National Security Adviser.
Mr Pompeo's arrival in Doha follows an address to the region delivered from Cairo on Thursday in which he pledged continuing US focus on stabilising the region and countering the threat posed by Iran and its role in Syria, Lebanon, Iraq and Yemen.