U.S. Secretary of State Hillary Rodham Clinton arrived today in Vientiane for a three-hour official stopover en route to Phnom Penh, where she is to attend several regional conferences. She was scheduled to first meet with Lao Foreign Minister Thongloun Sisoulith and then Prime Minister Thongsing Thammavong, Lao Foreign Affairs Ministry officials said. "The meeting with Thongsing promises to be pretty brief," a Lao official was quoted as saying by DPA. After the talks, she would visit the National Handicap Rehabilitation Center before departing for the Cambodian capital. "This groundbreaking visit to Laos marks the first by a Secretary of State in 57 years," the US State Department said.