* U.N. urges more aid access inside Syria to slow refugee waves
* Turkey urges setting up camps inside Syria under U.N. protection
* But other host countries reluctant, unwilling to antagonise Assad
By Suleiman Al-Khalidi
ZAATARI, Jordan, May 4 (Reuters) - The four main host countries for Syrian refugees said at a meeting on Sunday that only the wider distribution of aid inside Syria could curb an exodus that is putting huge strains on neighbouring states.
After talks at the Zaatari camp in Jordan with the U.N. high commissioner for refugees, ministers from Turkey, Iraq, Jordan and Lebanon urged the implementation of a U.N. resolution passed in February that demanded rapid unhindered access for aid.
"A crucial aspect of ending this crisis is to improve access for humanitarian aid inside Syria," High Commissioner Antonio Guterres told reporters. Aside from some 3 million refugees abroad, a further 6.5 million were displaced inside Syria and 3 million had minimal access to essential services, he said.
"This is the worst catastrophic humanitarian situation we are facing, probably since the Rwanda genocide," he added. "We are now clearly above 3 million Syrian refugees."
In just over three years, the conflict has killed over 140,000 of Syria's roughly 23 million people.
Turkey, deeply hostile to Syrian President Bashar al-Assad and host to 720,000 registered Syrian refugees, wants U.N. camps established inside Syria: "The U.N. system should establish camps within Syria for the internally displaced so that the refugee crisis would at least be under control," Foreign Minister Ahmet Davutoglu said after the meeting at Zaatari.
"But here the barrier is the regime."
Jordan and Iraq, less willing to antagonise Assad, do not share Turkish enthusiasm for internal camps. And Guterres said violence in the country would make it hard to set them up.
Davutoglu said humanitarian conditions had worsened since the U.N. aid resolution. A first convoy of 78 trucks that entered Syria in March after repeated U.N. requests to Damascus barely met a single day's requirements, he said.
Syria's government has let some supplies through crossings it controls with Lebanon and Jordan. It has traded blame with the rebels for problems getting aid to the worst battle zones.
New attacks, notably by crude "barrel bombs", were pushing more Syrians to flee the country, Davutoglu added.
Jordanian Foreign Minister Nasser Joudeh said the kingdom, dependent on aid itself, was barely coping with 1.3 million Syrians living among the country's seven million population.
"The pressures this is causing on resources and society are unprecedented and is stretching thin the abilities of the government to continue to provide for the refugees," he said.
Jordan has sharply reduced the influx of Syrians over the past year by closing the most accessible unofficial border crossings, forcing those fleeing the violence into long detours. (Editing by Alastair Macdonald)