(Adds Amano quote, details, background)
VIENNA, June 8 (Reuters) - The U.N.'s nuclear agency is studying a request from Syria to help convert an atomic reactor near Damascus to use lower grade nuclear fuel which would be harder to use in bombs, its head said on Monday.
The reactor is currently running on highly-enriched uranium (HEU) and Syria wants the help of the International Atomic Energy Agency to use low-enriched uranium (LEU) and to ship the higher-grade material abroad, Yukiya Amano told reporters.
"We have received a request from Syria early this year to convert the HEU fuel to LEU fuel and to repatriate the HEU to the country of origin. We are now studying this request," Amano told reporters, without giving further details.
Uranium enriched to less than 5 percent of fissile purity is usually considered low-enriched, while an atomic bomb would usually be based on 90-percent enriched uranium.
Chinese-designed so-called MSNR reactors, such as the one at the Syrian site, normally run on about 1 kilogramme of 90-percent enriched uranium, according to the IAEA - far less than what is needed for an atomic bomb.
Still, any loss or theft of highly enriched uranium, plutonium or other types of radioactive material is potentially serious as militants could try to use them to make a crude nuclear device or a "dirty bomb", experts say.
Syria has suffered under years of civil war and jihadist militants have brought swathes of its territory under their control.
In the IAEA's latest assessment on Syria, it said that a "physical inventory verification at the MNSR would be postponed until the security conditions had sufficiently improved."
The Syrian case has been on the agenda of the IAEA board's quarterly meetings for over six years.
The IAEA has long sought to visit a Syrian desert site where U.S. intelligence reports say a North Korean-designed reactor was being constructed to make plutonium for nuclear bombs, before Israel bombed it in 2007.
Syria has said the eastern site at Deir al-Zor was a conventional military base but the IAEA concluded in 2011 it was "very likely" to have been a reactor that should have been declared to anti-proliferation inspectors.
"I renew my call to Syria to cooperate fully with us in connection with unresolved issues related to the (Deir al-Zor)site and other locations," Amano said. (Reporting By Shadia Nasralla; Editing by Angus MacSwan)