(Reuters) - President Barack Obama's national security adviser has briefed Israel's Prime Minister Benjamin Netanyahu on a U.S. contingency plan to attack Iran [1] should diplomacy fail to curb its nuclear program, an Israeli newspaper reported on Sunday.

The Haaretz newspaper said that the U.S. adviser - Thomas Donilon - had described the plan in talks with Netanyahu earlier this month.

A senior Netanyahu aide, Harel Locker, refused to comment on the report when asked about it in an interview with an Israeli radio station. Another Israeli official reached by telephone, said "we do not comment on closed-door diplomatic meetings".