* Sources say money to be used for state diamond purchases
* State support may help Alrosa service debt
* Alrosa sought $3 billion in state purchases in 2009-10
(Adds sources on diamond purchases, quotes)
By Katya Golubkova
MIRNY, Russia, Aug 21 (Reuters) - Russian Prime Minister Vladimir Putin on Friday pledged $1 billion in state support for diamond miner Alrosa this year to help it ride out a steep global decline in demand for gemstones.
"The overall level of support for the sector should total 30-35 billion roubles ($949.4 million-$1.11 billion) this year," Putin told a meeting of senior officials after visiting Alrosa's giant Mir diamond mine in eastern Siberia.
"This is difficult to do with the background of the financial-economic crisis, but we shall do it," Putin said.
The state support, which will include more state purchases of gems, is likely to help state-controlled diamond miner Alrosa service about $3.6 billion in outstanding debt.
Two sources who declined to be identified said the $1 billion would be used by the State Precious Metals and Gems Repository (Gokhran) to buy diamonds from Alrosa.
Alrosa, the main rival to De Beers, produces one quarter of the world's rough diamonds and is one of the main sources of income for Russia's Yakutia region, home to 950,000 people.
"We understand that this sector, which gives serious revenues to the federal budget and regional budget, is in a difficult situation and needs support due to the global market situation," Putin said.
"To support the sector, the state has agreed to significantly increase state purchases of diamonds."
Putin said the state purchases by Gokhran had risen to 14.5 billion roubles from 3.7 billion roubles. Alrosa was seeking to sell Gokhran another $3 billion worth of gems during 2009-2010 to earn enough to service the company's outstanding debt.
"The support given by the state will allow Alrosa to fulfil its obligations and to finance its investment programme," a spokesman for the diamond maker said. Putin gave no details about state purchases planned for 2010.
Diamond producers across the globe have been badly hit by weak demand. The world's largest diamond producer, De Beers, which is 45 percent-owned by mining group Anglo American Plc, has said demand should pick up in the second half.
Alrosa President Fyodor Andreyev said on Friday he expected diamond demand would recover by 2011 as long as there were no second wave to the financial crisis.
Putin also ordered officials to work out a way to give a state guarantee to Alrosa to help it restructure its debts to domestic and foreign creditors.
DIAMOND CRISIS
Russia's economy is in the worst recession since the chaotic days of the 1990s and companies are asking the government for hundreds of billions of dollars in state support.
But with gross domestic product on course to decline by half a trillion dollars this year, officials say only major companies or those with particular social or political importance were likely to be bailed out.
Diamond sales make up 30 percent of the local government's revenue in Yakutia, which covers an area about one-third the size of the United States.
Alrosa, which traces its history to the diamond mines set up the Soviet Union in Yakutia in the 1950s, employs 15,000 people and produces 97 percent of Russia's rough diamonds.
"In recent years, $17.5 billion of diamonds have been found here (in Mirny) and about $80 billion in the republic as a whole, but when you work out how much has actually been invested here in the republic, in its infrastructure, the figures are really not very significant," Putin said.
"The problems come from this and have been mounting for decades," Putin said.
Alrosa sells more than half its polished diamonds in the U.S. market. Other major buyers of Alrosa's diamonds are located in Belgium, Israel and the United Arab Emirates. (Additional reporting by Polina Devitt; Writing by Guy Faulconbridge; Editing by William Hardy)