BEIRUT/WASHINGTON, May 26, 2018 (News Wires) - Lebanon expressed concern to Syria on Saturday over a new law aimed at redeveloping areas devastated by seven years of war, saying the initiative could hinder the return of many Syrian refugees to their homeland. Lebanese Foreign Minister Gebran Bassil wrote in a letter to his Syrian counterpart Walid al-Moualem that the terms of "Law 10" could make it difficult for refugees to prove property ownership, and in turn discourage some from returning. The legislation came into effect last month as the army was on the brink of crushing the last insurgent enclaves near Damascus, consolidating President Bashar al-Assad's grip over nearly all of western Syria. It allows people to prove they own property in the areas chosen for redevelopment, and to claim compensation. But aid groups say the chaos of war means few will be able to do so in the time specified. The law has yet to be applied. Bassil, whose country hosts more than a million Syrian refugees, voiced concern over the limited time frame given for refugees to prove possession of their properties. "The inability of the refugees to practically present what proves their possession (of their properties) during the given time limit might lead to them losing their properties and their sense of national identity," Bassil said in the letter, according to a Foreign Ministry statement. "This would deprive them of one of the main incentives for their come return to Syria," he added, echoing comments earlier this week by Lebanese Prime Minister Saad al-Hariri. Hariri said the law "tells thousands of Syrian families to stay in Lebanon" by threatening them with property confiscation. Bassil sent a similar letter to U.N. Secretary-General Antonio Guterres, calling for action to protect the rights of Syrian refugees in maintaining their properties. Meanwhile, the United States warned Syria on Friday it would take "firm and appropriate measures" in response to ceasefire violations, saying it was concerned about reports of an impending military operation in a de-escalation zone in the country's southwest. Washington also cautioned Syrian President Bashar al-Assad against broadening the conflict. "As a guarantor of this de-escalation area with Russia and Jordan, the United States will take firm and appropriate measures in response to Assad regime violations," State Department spokeswoman Heather Nauert said in a statement late on Friday. A war monitor, the Britain-based Syrian Observatory for Human Rights, reported on Wednesday that Syrian government forces fresh from their victory this week against an Islamic State (IS) terrorist groups pocket in south Damascus were moving into the southern province of Deraa. Syrian state-run media have reported that government aircraft have dropped leaflets on rebel-held areas in Deraa urging fighters to disarm. The U.S. warning comes weeks after a similar attack on a de-escalation zone in northeastern Syria held by U.S.-backed Syrian Democratic Forces (SDF). U.S. ground and air forces repelled the more than four-hour attack, killing perhaps as many as 300 pro-Assad militia members, many of them Russian mercenaries. Backed by Russian warplanes, ground forces from Iran and allied militia, including Lebanon's Hezbollah, have helped Assad drive rebels from Syria's biggest cities, putting him in an unassailable military position. They have recaptured all remaining insurgent areas near Damascus in recent weeks, including the densely populated eastern Ghouta area, as well as big enclaves in central Syria.