Trump's new statement on the connections of Qatar to the terrorist outfit of ISIS, which was proven by several other Arab countries, and thus this makes the country as a prime target who funds the ISIS against Saudi Arabia, UAE, Bahrain, and Egypt, as well as the US.
Qatar, which has developed an assertive foreign policy over the past decade, denied that it supports militants and said it was helping to reduce the threat of terrorism by backing groups that fight poverty and seek political reform.
Foreign Minister Sheikh Mohammed bin Abdulrahman Al Thani called the moves by Arab neighbours and others "clear violations of global law and worldwide humanitarian law".
"Qatar insisted on interfering in the domestic affairs of Egypt, Bahrain, and other Arab countries in a way that threatens their safety and security and harms Arab national security and unity", it added. The measures are more severe than during a previous eight-month rift in 2014, when Saudi Arabia, Bahrain and the UAE withdrew their ambassadors from Doha, again alleging Qatari support for militant groups.
Trump also called on "all the nations" to stop immediately supporting terrorism, "stop teaching people to kill other people", and "stop filling their minds with hate and intolerance".
"I want to call on all other nations to stop immediately supporting terrorism", Trump said. Turkey, like Kuwait, has offered to mediate.
With supply chains disrupted and concern mounting about economic turbulence, banks and firms in Gulf Arab states were trying to keep business links to Qatar open and avoid a costly firesale of assets.
Qatar said on Thursday the action against it was endangering stability in Gulf but it was not prepared to compromise to settle the dispute.
Trump's tweet appeared at odds with comments from USA officials who had said on Monday that the United States would quietly try to calm the waters between Saudi Arabia and Qatar because Qatar is too important to US military and diplomatic interests to be isolated.
The list includes Muslim Brotherhood's spiritual leader Yousuf al-Qaradawi and Doha-sponsored charities Qatar Charity and Eid Charity.
Officials from Qatar and its Gulf Arab neighbours embarked on a quickening round of shuttle diplomacy, with the Qatari foreign minister due in Moscow and Brussels and Bahrain's king visiting his ally Egypt for talks on the crisis.
In an interview published by Saudi-owned Asharq al Awsat newspaper, Bahraini Sheikh Khalid bin Ahmed al-Khalifa said conditions posed by the four countries for a resolution of the crisis were "crystal clear".
The UAE's General Civil Aviation Authority also announced on Twitter that it had "closed the airspace for all air traffic to and from Doha until further notice".
The two held talks, though details of their discussions were not released. Sheikh Sabah earlier Wednesday traveled to Dubai where he met with Abu Dhabi's Crown Prince Sheikh Mohammed bin Zayed Al Nahyan and Dubai's ruler Sheikh Mohammed bin Rashid Al Maktoum, who also serves as prime minister and vice president of the UAE.