After meeting with junta leaders in Myanmar, Jim Webb comes to Cambodia to talk about free trade with Hun Sen and free speech with opposition leaders.

US Senator Jim Webb said he "listened in great detail to the concerns of the opposition leaders" during a visit to Cambodia on Tuesday, but stopped short of condemning the government's ongoing crackdown on political speech.

Fresh from negotiating the release of an American prisoner with Myanmar's ruling military junta on Saturday, Webb met with opposition leaders Sam Rainsy and Kem Sokha, as well as Prime Minister Hun Sen, during his brief stopover in the Kingdom.

Kem Sokha, president of the Human Rights Party who was briefly imprisoned on defamation charges in 2006, said the US "should continue to monitor democracy in Cambodia because it is still not going smoothly."

He said that he did not present Webb with individual defamation cases during the meeting, but told the senator that freedom of expression has been an issue recently.

Webb met later in the day with Hun Sen and other government officials at the National Assembly. Eang Sophalleth, a spokesman for the prime minister, said afterward that talks focused on increasing cooperation between Cambodia and the US, particularly in the economic realm.

Hun Sen proposed that the US "continue helping Cambodia by allowing duty-free garment exports," Eang Sophalleth said, a proposal also floated to Webb by Commerce Minister Cham Prasidh in a morning meeting.

Webb said that Cham Prasidh "made a very compelling case" for US legislation to wave Cambodian garment duties, though he noted the importance of maintaining labour standards in the Kingdom's factories.

Cambodia is the fourth stop for Webb on a five-nation, two-week trip, the purpose of which, he said, is "to invigorate the relationship between the United States and all the countries of Southeast Asia." Some civil society groups, however, have been sceptical of Webb's capacity to generate meaningful reforms in the region.

Although Webb secured the release of American prisoner John Yettaw in Myanmar last week, opposition figure Aung San Suu Kyi remains in detention. Myanmar dissident groups last week released an open letter to Webb in which they expressed fears that the senator's visit would legitimise the ruling junta.

"We are concerned that the military regime will manipulate and exploit your visit and propagandise that you endorse their treatment of Daw Aung San Suu Kyi and over 2,100 political prisoners," read the letter from groups including the All Burma Monks' Alliance.

These same concerns are present as Webb meets with leaders in Cambodia, said Eleanor Nichol, a campaigner for the Global Witness rights group. "The danger here is that Senator Webb's visit will be used to support the current government's lip-service on its commitment to democracy, human rights [and] rule of law," Nichol said.

Sam Rainsy Party spokesman Yim Sovann, however, was pleased that Webb took time to hear concerns from all sides during his visit in order to gain a "balance of information". "This is the culture we would like," he said.