The Obama administration secretly gave its blessing to arms shipments to Libyan rebels from Qatar last year, but American officials later grew alarmed as evidence grew that Qatar was turning some of the weapons over to Islamic militants, according to United States officials and foreign diplomats.

No evidence has emerged linking the weapons provided by the Qataris during the uprising against Col. Muammar el-Qaddafi to the attack that killed four Americans at the United States diplomatic compound in Benghazi, Libya, in September.

But in the months before, the Obama administration clearly was worried about the consequences of its hidden hand in helping arm Libyan militants, concerns that have not previously been reported. The weapons and money from Qatar strengthened militant groups in Libya, allowing them to become a destabilizing force since the fall of the Qaddafi government.

The experience in Libya has taken on new urgency as the administration considers whether to play a direct role in arming rebels in Syria, where weapons are flowing in from Qatar and other countries.

The Obama administration did not initially raise objections when Qatar began shipping arms to opposition groups in Syria, even if it did not offer encouragement, according to current and former administration officials. But they said the United States has growing concerns that, just as in Libya, the Qataris are equipping some of the wrong militants.

The United States, which had only small numbers of C.I.A. officers in Libya during the tumult of the rebellion, provided little oversight of the arms shipments. Within weeks of endorsing Qatar’s plan to send weapons there in spring 2011, the White House began receiving reports that they were going to Islamic militant groups. They were “more antidemocratic, more hard-line, closer to an extreme version of Islam” than the main rebel alliance in Libya, said a former Defense Department official.

Canadafreepress has a 3 part interview on Benghazi that hits it .