He said Qatar needed to shut down or limit its Al-Jazeera news network, as well as stop funding extremist groups and others. "Perhaps this will be the beginning of the end to the horror of terrorism!" Trump wrote on Twitter.
"If we have to, these are all entanglements that we have to deal with as the crisis develops and create solutions to them and this will be a very, very sad course that we need to take, but I am hoping that cooler heads will prevail in Qatar".
Several Middle Eastern countries, including Saudi Arabia, Egypt and the United Arab Emirates, cut ties with the tiny Gulf state on Monday over what they say is Qatar's support for terrorism, a claim Qatar vehemently denies.
CNN reported Tuesday night that US intelligence officials also believe Russian hackers planted the fake story; FBI investigators were recently on the ground in Doha.
Qatar, a major player in the global gas industry and host to the biggest U.S. military base in the Middle East, has crafted an independently-minded foreign policy, attracting criticism for engaging with groups from Hezbollah to Hamas.
UAE airlines Etihad and Emirates said all travelers holding Qatari passports were now prohibited from traveling to or transiting through the emirates.
Soccer's world governing body Federation Internationale de Football Association also has said it remains in regular contact with Qatar, which will host the 2022 World Cup.
President Donald Trump injected the United States into a volatile crisis among America's Mideast allies, siding Tuesday with Saudi Arabia and other countries against Qatar in a dispute that threatens to disrupt efforts to defeat the Islamic State group and counter Iran.
He met his Saudi regime counterpart Adel al-Jubeir in Berlin on Wednesday. He said the "fairly large cost" on Qatar's economy would convince it to change its policies.
The multibillion-dollar preparations to host the 2022 tournament, which involve building nine stadiums and huge infrastructure, is put into perspective by local reports that Qataris are so anxious about the blockade that they are storming the supermarkets and leaving shelves empty of food. "In all battlefields, there are adversaries", he told the American TV channel.
Trump said he'd told the kings, presidents and prime ministers that funding "Radical Ideology" can't be tolerated, and "Leaders pointed to Qatar - look!" Both the leaders discussed ways to prevent terror financing and eliminate extremism by any country in region, the White House said yesterday.
Kuwait's Emir Sheikh Sabah Al-Ahmad Al-Jaber al-Sabah flew to Saudi Arabia for talks with King Salman bin Abdulaziz, Saudi and Kuwaiti state media reported, but gave no details on the discussions.
Sultan Sooud Al Qassemi's comments in an interview with The Associated Press came as Emirati officials also announced those offering support to Qatar online could face years in prison and fines for offering sympathy to the country, suggesting the crisis will only intensify.
The desert nation is heavily reliant on food imports, predominantly through its border with Saudi Arabia, where hundreds of trucks transporting food and construction materials have now been stopped from entering. "We believe any differences should be resolved at the negotiating table to eliminate concerns and unite forces against the main threat in the region, terrorism".
A Qatari official, however, said the rift was pushing Doha in the direction of leaving the six-state Gulf Cooperation Council, founded in 1981, "with deep regret".
Bans on Doha's fleet using regional ports and anchorages threatened to halt some of its exports and disrupt those of liquefied natural gas.