UNITED NATIONS (Reuters) - U.N. staff worldwide were warned on Tuesday to steer clear of the shards of weapons that may have been made with depleted uranium, blamed by some peacekeeping soldiers in Kosovo for cases of leukemia.

 The U.N. Office of Human Resources Management, in a letter to all personnel who served or were now serving in a region where depleted uranium weapons were used, said there was little evidence at present to suggest a link between the material and leukemia, a potentially fatal blood cancer.

 It pledged to continue monitoring the situation and quickly issue relevant medical advice as it became available and urged staff to get a check-up from the U.N. medical services if they felt they needed one.

 The weapons were used by a U.S.-led coalition in Iraq during the 1991 Gulf War and by NATO in the Balkans in the 1990s. Depleted uranium is used in the tips of missiles, shells and bullets to increase their ability to penetrate armor, but on impact it can break down into radioactive dust.

 The United Nations earlier this month said it found evidence of radioactivity at eight of 11 sites tested in Kosovo after they were struck by NATO ammunition with depleted uranium during 1999 bombings. More tests of soil, water and vegetation samples are under way, with results expected in March.

 But NATO insists the bombings pose no risk of a dread "Balkans syndrome," saying the depleted uranium used in the armaments gives off less than natural background levels of radioactivity.

 The World Health Organization expects to issue its own conclusions in late February after reviewing the available scientific evidence on the health effects of depleted uranium.

 Russia, which has seized on the controversy to berate NATO for alleged dirty tactics, charged on Wednesday that the environmental impact of NATO's 1999 bombing of Yugoslavia equaled that of the explosion at the Chernobyl nuclear plant, site of the world's worst nuclear accident in 1986.