"His message was that we need unity in the region to fight extremist ideology and terrorist financing", a USA official told Reuters news agency.
He later tweeted: "Perhaps this will be the beginning of the end to the horror of terrorism!"
A Qatari central bank official, declining to be named under briefing rules, told Reuters the riyal's dip was due to speculation and that Qatar had huge foreign exchange reserves which it could use if necessary to support its currency.
"Until the Iranian regime is willing to be a partner for peace, all nations of conscience must work together to isolate Iran, deny it funding for terrorism, and pray for the day when the Iranian people have the just and righteous government they deserve", he said during his speech.
"What is happening is the preliminary result of the sword dance", tweeted Hamid Aboutalebi, deputy chief of staff of Iran's President Hassan Rouhani, referring to news photos of Trump's traditional dance with the Saudi king during last month's Riyadh summit.
"During my recent trip to the Middle East I stated there can no longer be funding of Radical Ideology", Trump said on Twitter Tuesday.
Qatar was also expelled from the Saudi-led coalition fighting Iranian-backed Houthi rebels in Yemen.
"I think the Qataris want an off-ramp, but if you're the Saudis, are you going to back off your maximalist demands at this point?"More news: Schindler prepares for party after seeing Huddersfield into Premier League
Author and political activist David Swanson said that the United States, Saudi Arabia and Qatar all claimed to be fighting extreme Islamist terror but all three of them continues d to support it. "It has to choose whether it must move in one direction or another direction".
Moreover, the country also has close ties with Qatar itself.
He name-checked "support of extremist groups", "hostile media" and "interference in affairs of other countries" as things Qatar would have to change if it wished to restore ties.
Maersk MAERSKb.CO, the world's biggest container shipping line, said it was unable to transport goods in or out of Qatar because it could not take them through the UAE port of Jebel Ali.
The Muslim Brotherhood in Egypt is another Islamist group that became politically active.
In 2009, then-Secretary of State Clinton declared in a diplomatic cable that "donors in Saudi Arabia constitute the most significant source of funding to Sunni terrorist groups worldwide".
What is happening in Qatar?
A former USA diplomat in the region said the inconsistencies between Trump's tweets Tuesday and Tillerson and Mattis's statements Monday would make it hard for US diplomats to do their jobs.More news: White House: Trump won't stop Comey from testifying
Foreign Minister Sheikh Mohammed bin Abdulrahman al-Thani told Qatar-based Al Jazeera TV Qatar would not retaliate, hoping Kuwait would help resolve the dispute.
The Arab countries have blocked Qatari vessels from entering their airspace, as well as using their seaports as Saudi Arabia has closed off its land border.
The United States has about 8,000 to 10,000 troops at Udeid Air Base in Doha, Qatar's capital.
Flight tracker websites showed Qatar Airways flights taking a circuitous route mostly over Iran to avoid their neighbors.
The deal, which was concluded in April, heightened concerns among Qatar's neighbours about the small gas-rich state's role in a region plagued by conflict and bitter rivalries.
Addressing foreign ambassadors at a Ramadan dinner Tuesday, President Recep Tayyip Erdogan commended Qatar for what he called a "cool-headed and constructive" stance in the dispute and said Qatar is leading an "effective fight" against terrorist groups.
Meanwhile, State Department spokesman Heather Nauert tried to soften Mr. Trump's comments on Qatar this week.More news: India to take ties with Spain to new level: Modi
France's President Emmanuel Macron spoke to Mr Erdogan and to the emir of Qatar in separate telephone calls, saying he was ready to back "all initiatives to encourage calm".