PHNOM PENH, Cambodia (AP) - Cambodia's self-exiled opposition leader has vowed to return to Cambodia ahead of this month's general election to help challenge the 28-year rule of Prime Minister Hun Sen. The government says Sam Rainsy is welcome home but could face arrest if he returns. Sam Rainsy made the announcement Sunday in a letter to the international community from France where he is living to avoid a 12-year prison sentence on charges widely seen as politically motivated. The opposition leader is barred from running for office due to his conviction. He says his return will test whether the elections are "free and fair," as the government claims. U.S. lawmakers are pushing to cut the more than $70 million in annual American aid to Cambodia if Hun Sen wins the July 28 vote.