At the Friends of Syria meeting in Paris, Clinton joined other governments in calling for a new Security Council resolution under Chapter 7 of the U.N. Charter, which in some circumstances could authorize military intervention in Syria. (Jason Reed/AFP/Getty Images)

Secretary of State Hillary Rodham Clinton arrived in Kabul on Saturday morning, a brief stopover before she heads to a conference in Tokyo on aid to Afghanistan.

Before having breakfast with Afghan President Hamid Karzai, she announced that the administration has declared Afghanistan a major non-NATO ally of the United States.

This was Clinton’s first visit since President Obama and Karzai signed an agreement May 1 that commits the United States to supporting Afghanistan for the next decade in economic development, rule of law and security, among other areas, as U.S. and NATO forces withdraw from the country.

On Friday in Paris, Clinton denounced Russia and China for “blockading” international efforts to bring an end to the Syrian crisis, as confirmation reached a Friends of Syria meeting there that a powerful Syrian military officer had defected from the government of President Bashar al-Assad.

French Foreign Minister Laurent Fabius told high-ranking representatives that Maj. Gen. Manaf Tlas, a longtime member of Assad’s inner circle, had fled Damascus. In a news conference later Friday, Clinton seized the moment to encourage others close to Assad to do the same.

“The Syrian people will remember the choices you make in the coming days, and so will the world,” Clinton said. “It is time to abandon the dictator, embrace your countrymen and women, and get on the right side of history.”

News of the high-level defection amounted to a glimmer of good news for more than 80 nations and international organizations trying to salvage an effort by U.N. envoy Kofi Annan to end the 16-month uprising in Syria, where the situation is steadily deteriorating.

Clinton told the conference that Russia and China, which had declined invitations to attend, “are holding up progress — blockading it — [and] that is no longer tolerable.” The chief U.S. diplomat said Moscow and Beijing were not “paying any price at all — nothing at all — for standing up on behalf of the Assad regime,” and she urged the two veto-wielding U.N. Security Council members to support a new U.N resolution based on the Annan proposal that they endorsed in Geneva last weekend.

Her comments reflected rising frustration, in particular, with the government of Russian President Vladimir Putin, which has steadfastly refused to abandon Assad or even cut its ties with him, despite signing on to Annan’s plan.

The United States and others pushing for Assad’s ouster remain reluctant to intervene directly in Syria, especially without an international legal mandate, which Russia has blocked at the United Nations. Annan’s plan calls for a transitional government based on the “mutual consent” of opposition groups and members of the Syrian government.

Russia, the Syrian government’s principal arms supplier, has interpreted that language to mean that Assad might remain in power in a newly constituted government. U.S. officials, however, have insisted that “mutual consent” means opposition leaders could veto participation by Assad or others “with blood on their hands” — a point that Clinton emphasized Friday.

“Today the international community sent a clear and unified message: The violence in Syria must stop, a democratic transition must start and Assad must go,” Clinton said. She said support for the Annan plan “dispelled any doubt about Assad’s role in a transition: He has none.”

Syrian opposition factions have said Assad’s departure must be a precondition of any agreement.

The envisaged new resolution, under Chapter 7 of the U.N. Charter, could in some circumstances authorize military intervention in Syria. It would also impose global sanctions against Syria, including an arms embargo, and demand Assad’s cooperation with Annan’s plan.

Russia has vetoed two previous Security Council resolutions, along with China. It has also rejected any arms embargo that did not also apply to rebel forces in Syria. The way forward is further complicated as the situation in Syria continues to deteriorate and opposition groups struggle to present a unified front.

Human Rights Watch recently described an “archipelago” of torture centers operating around the country, and the head of a U.N. monitoring group said violence has reached “unprecedented” levels. On Friday, activists said that Syrian forces had killed at least 25 people and arrested scores of others during an operation to seize the northern rebel-held city of Khan Sheikhoun, according to the Associated Press.

A meeting this week of more than 30 opposition groups and other Syrian exiles in Cairo, intended to convey unity ahead of Friday’s conference, degenerated into chaos and fistfights before most of the disparate groups finally agreed on a plan demanding Assad’s removal and outlining a transitional government, elections and a constitutional referendum.

One opposition leader told the conference Friday that while Syrian rebels seem to have “many friends,” Assad remains in power and continues his crackdown.

“We would like your friendship to be efficient, effective — to help us put an end to this massacre,” said the opposition leader, whose name was not distributed to reporters.

Clinton met with four opposition leaders at the conference, including longtime dissident Riad Seif and Khaled Abu Saleh, a member of the Homs Revolutionary Council who recently left Syria.

Karen DeYoung in Washington contributed to this report.