* U.N. policy allows govt to use sieges as weapon -report
* Syria Campaign says aid situation could extend the war
* U.N. says is getting more through to besieged areas
By John Davison
BEIRUT, June 15 (Reuters) - A campaign group accused the United Nations on Wednesday of letting the Syrian government dictate how aid is distributed, denying food to thousands of starving civilians and potentially extending the war.
The Syria Campaign, which opposes President Bashar al-Assad, said that, by seeking government approval before making aid deliveries, the U.N. was allowing Damascus to ensure desperately hungry Syrians in besieged rebel-held areas were not reached.
"The U.N. has provided the Syrian government with an effective veto over aid deliveries to areas outside of government control, enabling its use of sieges as a weapon of war," the group, which advocates for peace and democracy in Syria, said.
"By choosing to prioritize cooperation with the Syrian government at all costs, the U.N. has enabled the distribution of billions of dollars of international aid to be directed by one side in the conflict," it said.
Aid agencies have recently reached areas that have been inaccessible for years but continue to struggle to get supplies to besieged areas where hundreds of thousands of Syrians live.
The U.N. said surgical equipment has been removed from some deliveries, something Jan Egeland, chairman of a U.N.-backed task force on humanitarian aid, said violated international law.
In its report "Taking Sides: The United Nations' loss of impartiality, independence and neutrality in Syria", based on interviews with U.N. officials and others, the Syria Campaign said U.N. aid policy "has contributed to the deaths of thousands of civilians".
"It has also led to the accusation that this misshapen U.N. aid operation is affecting - perhaps prolonging - the course of the conflict itself," it said.
The U.N. humanitarian coordinator in Syria said countries with influence over the warring sides were helping aid efforts and more besieged areas would be reached in the coming weeks.
"We use (those countries') leverage ... to create more space for us to do our work," Yacoub El Hillo said.
"Political pressure is paying off, and is creating humanitarian space for us to do our work."
Hillo said that for cross-border aid deliveries to areas not controlled by the government, the United Nations simply "notifies" the government, rather than seeking permission. In government-held areas, it is necessary to work with Damascus.
"The option is to engage with this government and to seek to reach these places, as we do ... it is not just by bulldozing our way through checkpoints, because that won't work," he said.
Nearly 600,000 people are besieged in 19 areas in Syria, with two-thirds trapped by government forces and the rest by armed opposition groups and Islamic State militants, according to U.N. estimates. (Additional reporting by Tom Perry; Editing by Robin Pomeroy)
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