Senior officials from Qatar have strongly denied claims the country is supporting extremist groups in Syria such as the Islamic State.
Speaking to the BBC, the officials said Qatar had provided support to moderate groups only, in co-ordination with the CIA and other Western and Arab intelligence agencies.
Strict financial controls had been put in place, they added.
In the past, the Qatari government and donors from the country are believed to have financed and armed hardline Islamist groups in Syria.
Doha is also believed to have links to the Al-Nusra Front, an Al-Qaeda affiliate.
Earlier this month a number of British MPs were reported to have questioned the UK’s closeness to Qatar, amid claims of the links to IS.
BBC security correspondent Frank Gardner says Qatar, a major investor in the UK through its sovereign wealth fund, has been stung by the allegations.
Last week US Treasury official David Cohen said Qatar, along with Kuwait, was not doing enough to choke off funding for extremist groups. His department has imposed sanctions on individuals in Qatar for allegedly funding designated terror groups in countries including Syria.
The Qatari denial came ahead of a visit to the UK this week by Qatar’s ruler Sheikh Tamim bin Hamad Al-Thani.
The officials, including Qatar’s director of intelligence, told the BBC the country had nothing to hide over its support for groups in Syria fighting President Assad’s regime.
The BBC’s Frank Gardner said the officials conceded that there had been constant shifts in allegiances in Syria’s civil war and some people previously considered moderate had later joined hard line Islamist militias.
They said that since Qatar’s intelligence agency had taken over responsibility for its Syria policy in 2012, new financial controls have been brought in and a number of suspect financiers have been arrested.
Since September, Qatar has been supporting the US-led military action against IS in Syria.
The Al-Udeid Air Base, a highly-classified US facility from which all attack and surveillance missions in the region are co-ordinated by US Central Command, is located in the emirate.