Sens. John McCain (R-Ariz.) and Joe Lieberman (I-Conn.) today visited a Syrian refugee camp on the Turkish-Syrian border and called on the United States to take an increased role in trying to unseat Syrian President Bashar al-Assad.

Their visit to the camp in Turkey’s Hatay province came a day after Syrian forces shot across the border into another refugee camp and on the same day as the United Nations’ deadline for officials in Damascus to withdraw forces as part of a cease-fire brokered by former U.N. head Kofi Annan.

McCain and Lieberman questioned the effectiveness of the cease-fire accord advocated by Annan, who was named the U.N.-Arab League envoy to Syria in February.

“Make no mistake: The situation in Syria is an armed conflict. This is a war. Diplomacy with Assad has failed, and it will continue to fail so long as Assad thinks he can defeat the opposition in Syria militarily,” McCain and Lieberman said in a joint statement. “And right now, using tanks and artillery and even attack helicopters, Assad has the upper hand on the battlefield.

“The only way to reverse this dynamic is by helping the Syrian opposition to change the military balance of power on the ground,” the statement continued. “The choice we have is very clear: Will the world continue to stand by while Assad kills thousands and thousands more people — or will we summon the resolve and the courage to do what it takes to stop the killing and force Assad to leave power?”

McCain and Lieberman, in conjunction with Sen. Lindsey Graham (R-S.C.), have taken the lead on challenging the administration’s level of engagement in Syria and unveiled a resolution at the end of March condemning violence in Syria while also calling on the president to do more to ameliorate the situation in the region.

In their statement today, McCain and Lieberman called on an increased demonstration of “leadership” but fell short of asking for specific military action, such as air strikes or ground forces.

“It was clear during this visit that the Syrian people and our friends in this region are looking to the United States for leadership on Syria, and unfortunately, they are not finding it,” the statement read. “If America still stands for the cause of oppressed people who are fighting for their freedom, and justice, and deliverance from tyranny, we cannot abandon the people of Syria. We cannot shirk our responsibility to lead.”

According to the U.N., more than 9,000 people have been killed in Syria since peaceful protests against the Assan regime began more than a year ago.