Sean McCormack, US state department spokesman, said in Washington that the US welcomed the move, but said it was not enough.
"We see this as a step in the right direction, but it's not a substitute for the ability of our diplomats, as well as others, to travel not only to Lhasa, but into the surrounding area specifically," he told reporters.
China has insisted its response to the protests, the biggest challenge to its rule of Tibet in decades, has been restrained and that it has brought the situation under control.
The diplomatic trip comes on the heels of a surprise protest by Buddhist monks during a tightly-controlled tour of Tibet by foreign reporters.
On Thursday, monks at one of Tibetan's holiest shrines, the Jokhang temple in the heart of old Lhasa, embarrassed Chinese authorities when they spoke out in front of foreign reporters against China's rule of Tibet.
Ezzat Shahrour, a Beijing-based Al Jazeera correspondent who was one of the visiting reporters, said a group of monks interrupted the government-led tour and shouted for the return of the Dalai Lama and the freeing of detained monks.
Foreign journalists are generally not permitted to travel to Tibet.
All monasteries in Lhasa remain closed, a government official said, amid reports that monks had been held inside for more than two weeks.
"None of the monasteries in Lhasa are open... it's hard to say when they will reopen. This issue is beyond our powers," an official with the Lhasa tourism administration told AFP on Friday.
China has deployed huge contingents of security forces to quell unrest that has spilled from Lhasa to other areas of western China with Tibetan populations.
Anger in Nepal
While authorities have maintained firm control of dissent in China, activists have expressed their anger in other parts of the world.
A group of about 18 protesting Tibetans broke into the United Nations compound in the Nepalese capital of Kathmandu on Friday, while nearly 100 others protested outside.
|China says religious freedom has improved in|
Tibet under Beijing's rule [GALLO/GETTY]
Police arrested 60 of the protesters and dragged them away to waiting vehicles.
Activists have criticised the government of Nepal, which is home to thousands of Tibetan exiles, for stopping such protests.
Nepalese officials have responded that they cannot allow any activities against friendly nations, including neighbouring China.
The March 14 riots in Lhasa were preceded by four days of peaceful protests held to mark the anniversary of a failed 1959 uprising against Chinese rule.