US Secretary of State John Kerry expressed confidence on Tuesday that weapons being supplied by Gulf countries to the Syrian rebels were reaching the "right people," as he visited key rebel ally Qatar.
"We had discussions about the type of weapons that are being transferred. We are aware of what people are doing," Kerry told reporters in Doha at a press conference with Qatari Prime Minister Sheikh Hamad bin Jassem Al-Thani.
The new top US diplomat was on the last leg of his maiden Gulf tour, with the Syrian conflict topping the agenda, amid concerns over arms reportedly being supplied to Syria's insurgents by Gulf countries, including Qatar, falling into the hands of jihadists.
"We did discuss the question of the ability to try to guarantee [that the weapons] are going to the right people and to the moderate Syrian opposition coalition," he added, while repeating earlier comments on the impossibility of ensuring that.
On Monday, Kerry said in Abu Dhabi that "there is no guarantee that one weapon or another might not fall into the wrong hands."
The United States has so far refused to arm Syrian rebels locked in a two-year war against President Bashar al-Assad's loyalists.
But Kerry had said during a visit to Riyadh that Washington was working with its "friends to empower the Syrian opposition," while stressing it was not arming the rebels.
Several oil-rich monarchies of the six-member Gulf Cooperation Council, notably Saudi Arabia and Qatar, have supported the rebellion against Assad, a staunch ally of their regional foe Iran.
GCC members are dissatisfied at the refusal of US President Barack Obama's administration to arm Syrian rebels and its perceived lenient attitude towards Tehran, analysts say.
Kerry is due to wrap up his regional tour on Wednesday after visiting Qatar, the United Arab Emirates, Saudi Arabia, Egypt and Turkey.