UNITED NATIONS - The United Nations said on Thursday proposals to set up secure safe zones in Syria to help end the 17-month conflict raised "serious questions" and would need to be studied carefully.Ahead of a meeting on the humanitarian situation in Syria, France and Britain warned Syria's President Bashar Assad that military action to secure buffer zones for civilians inside the country was an option.Turkish Foreign Minister Ahmet Davutoglu, who is attending the meeting, urged the United Nations on Wednesday to protect displaced Syrians inside their country, but Assad dismissed talk of a buffer zone.Creating a buffer zone for displaced Syrians would be difficult because a U.N. Security Council resolution would be needed to set up a no-fly zone to protect the area, and Russia and China would not approve such a move, diplomats said.It is not the first time Russia has posed difficulties for the United States and its allies on the Security Council. In the 1990s, Moscow strongly supported Serbia in the Balkan Wars and acted as Belgrade's protector on the council.After an ineffectual UN presence failed to stop genocide in the 1992-1995 Bosnian War, the United States and its European allies infuriated Russia by bypassing the deadlocked Security Council and turning to NATO to halt the Serbian onslaught in Kosovo with a bombing campaign against Serbia in 1999.As Syria spirals deeper into a civil war, the 15-member council is paralyzed as Russia and China have blocked three Western-backed resolutions that criticized Assad and threatened sanctions.France, which is council president for August, had hoped the body could unite to deal with a shortfall in humanitarian aid and convened Thursday's meeting, which will also be attended by ministers from Syria's neighbors Turkey, Lebanon, Jordan and Iraq."If Assad falls quickly, then the reconstruction can take place, but if sadly the conflict continues then we have to examine various solutions. We have to be realistic," French Foreign Minister Laurent Fabius told the joint news conference with Hague."Such proposals raise serious questions and require careful and critical consideration," Deputy Secretary-General Jan Eliasson said at the start of the ministerial meeting.While the Security Council impasse between western nations and Russia and China means a resolution to approve such a move appears impossible, countries could act outside the authority of the world body and intervene, as happened in Kosovo in 1999."We're ruling nothing out and we have contingency planning for a wide range of scenarios," British Foreign Secretary William Hague told a news conference at the United Nations ahead of a meeting of Security Council foreign ministers later on Thursday to discuss how to ease Syria's humanitarian crisis."We also have to be clear that anything like a safe zone requires military intervention and that of course is something that has to be weighed very carefully," Hague said.