French President Nicolas Sarkozy urged Syria on Tuesday to exert pressure on its ally Hamas in order to help end the fighting in the Gaza Strip between the Palestinian group and Israeli forces. Meanwhile, his Syrian counterpart Bashar Assad slammed the Israeli assault on the coastal strip as a "war crime" and "barbaric," an "aggression" that Israel must halt. Sarkozy's visit to the Syrian capital is part of a whirlwind Mideast tour amid European diplomatic efforts to push a cease-fire proposal to stop Israel's expanding ground and air offensive on the Hamas-ruled area. More than 550 people have been killed since the assault began on December 27. Speaking to reporters at a joint press conference with Assad, Sarkozy urged the parties to move forward to end the fighting in Gaza and stressed there can be no military solution for the conflict, now in its 11th day. "Pressure should be exerted on all parties involved, including Hamas, in order for the guns to fall silent and peace to return," Sarkozy said. "President Bashar Assad can play a major role in this. Syria must help us to convince Hamas to choose the voice of reason and peace." Syria, along with Iran, is a major back of Hamas and Damascus hosts the exiled political leadership of Hamas and other radical Palestinian factions. Assad said he agreed with Sarkozy on the need for a quick resolution to the "humanitarian tragedy" and for a cease-fire, Israeli withdrawal and the lifting of Gaza's siege. Assad made no mention of Hamas ceasing to attack Israel. "What is happening is a war crime," he said of the Israeli ground and air assault on Gaza, adding that Israel will not be able to finish off Hamas. Sarkozy stressed there can be no return to the way things were when Hamas fired rockets into Israel. "Returning to the status quo as it was before is unacceptable by all sides," Sarkozy said. "Israel wants to guarantee its security and the Palestinians in Gaza want the reopening of the crossings ... We must replace spiral of violence with spiral of peace in Gaza." "Firing rockets on Israel is unacceptable and must stop," Sarkozy added. He called for sending immediate humanitarian aid to Gaza and underlined the need for opening "horizons fast to resume peace negotiations." Sarkozy has also talked with Egyptian President Hosni Mubarak, Israeli leaders and Palestinian Authority President Mahmoud Abbas during the ctour. His next stop is Lebanon. Along with Sarkozy, an EU delegation, including policy chief Javier Solana has been touring the region. Solana attended the press conference by the Syrian and French presidents. During a stop in Egypt Monday, Solana said European monitors who were once on Gaza's border with Egypt would be ready to return to work at the crossing after a cease-fire in Gaza is achieved.