By Tom Keatinge
Centre for Financial Crime and Security Studies
The dispute that has seen Saudi Arabia and its Gulf allies isolate Qatar stems from allegations that the tiny gas-rich nation is sponsoring extremist groups which are destabilising the Middle East.
This is not the first time Qatar's neighbours have expressed their displeasure over its individualist foreign policy - diplomatic relations were severed for nine months in 2014.
Tensions have arisen from Qatar's support for the Islamist Muslim Brotherhood; its close relationship with groups such as the Taliban and certain al-Qaeda affiliates; and its relationship with Iran, which has most recently led to allegations from Saudi Arabia that the state-funded broadcaster Al Jazeera is supporting Houthi rebelsin Yemen fighting government forces backed by Saudi Arabia and the United Arab Emirates.
Doha has strongly denied Riyadh's accusations, and said it has taken more robust counter-terrorism measures than some of its neighbours.
Yet this latest row is shining a particular light on the role Qatar plays with its immense wealth.
In April, it reportedly paid a ransom of as much as $1bn (£790m) to a former al-Qaeda affiliate in Syria and to Iranian security officials as part of a deal that resulted in the release of 26 royal family members reportedly kidnapped by Iranian-backed Iraqi Shia militiamen and of dozens of Shia fighters captured by jihadists in Syria.
Thus it is Qatar's alleged continued funding of radical ideology and extremism that is seemingly the cause of concern this time.
'Way to go'
Since 9/11, the United States-led global effort to disrupt terrorist financing has been relentless. Domestic laws and United Nations Security Council Resolutions have been passed; entities and individuals have been subject to national and UN sanctions; and suspected conduits for terrorist funding, such as remittance companies and charities, have been shut down.
But despite all this, the commitment of some key nations, including Qatar, has been repeatedly questioned.