He said his recent visit to Saudi Arabia was "already paying off" and the development might mark the "beginning of the end to the horror of terrorism".
Saudi Foreign Minister Adel al-Jubeir said Qatar must "change their policies" and stop supporting "extremist groups".
White House spokesman Sean Spicer said the United States is communicating with all the parties in the Middle East "to resolve issues and restore cooperation" over the Qatar dispute.
Commodities traders have grown concerned Qatar's LNG could be barred from Saudi Arabia or from traversing Egypt's Suez Canal, though so far no limitations have been imposed. Mr Trump tweeted on Tuesday.
Without much specificity, the White House said Trump called King Salman bin Abdulaziz Al Saud of Saudi Arabia on Tuesday and discussed the "critical goals of preventing the financing of terrorist organizations and eliminating the promotion of extremism by any nation in the region".
2002 Qatar's vast al-Udeid Air Base becomes a major hub for US forces fighting in Afghanistan and the later USA -led invasion of Iraq.
"We firmly believe these are unjustified measure (s) by the authorities in the kingdom against the network and its operations", the statement said. Erdogan, who has long tried to play the role of a regional power broker, said Ankara would do everything in its power to help end the regional crisis.
Saudi Arabia and its Gulf allies may have felt emboldened by Trump's visit, which saw the new president clearly align U.S. interests with Riyadh and lash out at Iran.
Back in 2014, Saudi Arabia, Bahrain and the UAE withdrew their ambassadors from Qatar in protest at what they called Doha's "interference in their internal affairs".
The emirate has, directly and indirectly, supported Islamist groups across the Arab world, including the Muslim Brotherhood.
Bill Cosby's lawyers claim race bias in jury selection
More than 50 women have come forward over the last two years accusing Cosby of rape and sexual assault decades ago. At times using a cane, Cosby watched jury selection closely this week, conferring often with his defense team.
Businesses sector say it is too early to gauge the impact from the Arab break-up with on Qatar.
In an interview with Doha-based satellite news network Al-Jazeera, Foreign Minister Sheikh Mohammed Bin Abdulrahman Al Thani said Kuwait's ruler had asked Qatar's emir to hold off on giving a speech about the crisis late Monday night.
The Turkish parliament was also set to bring forward approval of a draft accord between the two countries on military training cooperation, the officials said. Navy Capt. Jeff Davis, a Pentagon spokesman, expressed gratitude to Qatar for supporting the US presence, outlining no plans to adjust American military posture. The Qataris, Saudis and Kuwaitis have all funded extremists in the Syria conflict. "It will be quite complex to disentangle, but we are intent on saying we can not go back to the status quo ante", Gargash, the UAE minister, told Reuters in an interview.
Qatar says it intends to take legal action against those responsible.
Whatever the case, the Pentagon doesn't share Mr Trump's tone of triumphalism. More than 1 million Filipinos live and work in Saudi Arabia, Qatar and Bahrain.
Disruption to airspace in the Gulf began on Tuesday morning local time.
DOHA-BOUND - Overseas Filipino workers queue at a Qatar Airways check-in counter at the Ninoy Aquino International Airport for a flight to Doha Wednesday.
Flights to Europe and the Americas "are now not affected", the airline said.
Saudi Arabia said it revoked Qatar Airways' operating licenses and closed the airline's offices in the kingdom. Saudi Arabia, Bahrain and Egypt banned Qatari planes from landing and forbade them from crossing their air space.
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