US ambassafor Locke, who took a rare trip with his family, several embassy officials and Chengdu's consulate general, also stressed the need to open up access to Tibet to foreign diplomats, tourists and journalists, the embassy said in a statement.
US Embassy deputy spokesman Justin Higgins said it was the first time Chinese authorities had approved an embassy request to visit Tibet since September 2010.
The embassy said that in his meetings, Locke lobbied for opening access to Tibet to foreign diplomats, journalists and tourists and stressed the "importance of preserving the Tibetan people's cultural heritage, including its unique linguistic, religious and cultural traditions."
"We remain concerned by the deteriorating human rights situation in Tibetan areas, including the tragic self-immolations. The US urges Beijing to engage in substantive dialogue with the Dalai Lama or his representatives without preconditions," Higgins said.
'Locke concluded his six-days trip to Tibet Friday, June 28, Patrick Ventrell,' told reporters at his daily news conference.
"Ambassador Locke met with local officials, including the Tibet Autonomous Region Party Secretary Chen Quanguo and Lhasa Party Secretary Qizhala. He met with leading monks from a number of Lhasa monasteries that attended his meetings with Secretary Chen," Ventrell said.
"He also called on TAR (Tibetan Autonomous Region) authorities to preserve Tibet's language, culture, and religion, and expressed our deep concerns over self-immolations," he said.
US ambassador to China visited Ngaba in north-eastern Tibet in September 2012, where most of the self-immolation protests have taken place. Locke met with government officials and local residents during a stop in Ngaba county.
Beijing has imposed tight restrictions on foreign diplomats, the international media and tourists from visiting Tibet.
Since 2009, over 119 Tibetans have set themselves in protest against the repressive rule of the Chinese government. The self-immolators have called for the return of His Holiness the Dalai Lama to Tibet and freedom for Tibetans.