STATE DEPARTMENT - U.S. Secretary of State John Kerry says the Syrian military's siege of Qusair risks widespread civilian casualties.

With fighting for control of the border town of Qusair now in its third week, Kerry says civilians are under near-constant assault by forces of President Bashar al-Assad and allies from Iran and the Lebanese-based militant group Hezbollah.

"Today in Qusair, which is under siege by his forces and the surrogate forces, you have an extraordinary number of civilians who are trapped, and he will not allow the Red Cross and humanitarian aid to go in until the military has finished what it intends to do," he said.

Kerry says President Assad's conduct is unacceptable by any standard. "The world is seeing the actions of a person who has lost touch with any reality except his own and who is willing to wreak any kind of punishment on the people of his country simply so that he can maintain power," he said.

Kerry says "all civilized countries" call on President Assad to engage in a legitimate peace process "by which the people of Syria can protect minorities, be inclusive, and have the people of Syria decide their future."

"This is a very difficult process which we come to late. We are trying to prevent the sectarian violence from dragging Syria down into a complete and total implosion where it has broken up into enclaves and the institutions of the state have been destroyed with God knows how many more additional refugees and how many innocent people killed," he said.

The United States and Russia are pushing for face-to-face talks between representatives of the Assad government and its opponents to establish a transitional authority for Syria.

Russian Deputy Foreign Minister Sergei Ryabkov said Monday that the United States is not putting enough pressure on the Syrian opposition to participate in the international talks and to drop its demand for President Assad's exit.

The Syrian government has said it is willing to attend such a conference in principle. But the main opposition coalition has rejected the idea, saying talks are meaningless while Syrian, Hezbollah, and Iranian forces commit alleged atrocities against the Syrian people.

Kerry says Russia's planned sale of advanced missile technology to Assad forces could put prospects for a peace conference at risk.

He says U.S. Undersecretary of State for Political Affairs Wendy Sherman will travel to Geneva Tuesday to meet with Russian counterparts "to continue to lay the groundwork for the possibility of a negotiated resolution."