Turkey has brought forward troop deployment to Qatar and pledged to provide crucial food and water supplies to the Gulf Arab country facing a worsening rift with its powerful Middle Eastern neighbours.

The move is seen as a sign of Turkish support for Qatar after Saudi Arabia, the UAE, Egypt and Bahrain, among other states, cut diplomatic ties and major transport links with the gas-rich emirate.

They accused Qatar of funding militant groups - allegations it vehemently denies.

Turkey set up a military base in Qatar, its first such installation in the Middle East, as part of an agreement signed in 2014.

Turkey has close ties with Qatar, including in the energy sector, but also maintains good relations with other Gulf countries.

Turkish President Tayyip Erdogan has said isolating Qatar will not resolve any problems adding that he intends to "develop" ties with the embattled Gulf state.

Turkey has also pledged to provide crucial food and water supplies to Qatar.

US President Donald Trump offered offered to help resolve the worsening diplomatic crisis between Qatar and other Arab powers as the United Arab Emirates invoked the possibility of an economic embargo on Doha over its alleged support of terrorism.

In his second intervention in the row in as many days, Mr Trump urged action against terrorism in a call with Qatari Emir SheikhTamim bin Hamad al-Thani, a White House statement said.

"The President offered to help the parties resolve their differences, including through a meeting at the White House if necessary," it said.

Mr Trump, in a later call with Abu Dhabi's crown prince, Sheikh Mohammed bin Zayed al-Nahayan, called for unity among Gulf Arabs "but never at the expense of eliminating funding for radical extremism or defeating terrorism," the White House said.

In a sign of economic damage from the dispute, Standard & Poor's downgraded Qatar's debt yesterday as the country's riyal currency fell to an 11-year low amid signs that portfolio investment funds were flowing out because of the rift.

S&P cut its long-term rating of Qatar by one notch to AA- from AA and put the rating on Credit Watch with negative implications, meaning there was a significant chance of a further downgrade.

UAE Minister of State for Foreign Affairs Anwar Gargash told Reuters there would be more economic curbs on Qatar if necessary and said Doha needed to make ironclad commitments to change what critics say is a policy on funding Islamist militants.

He later told France 24 television that any further steps could take the form of "a sort of embargo on Qatar".