US Secretary of State John Kerry on Tuesday welcomed Cambodia's booming economic growth but also expressed concerns about the Southeast Asian nation's human rights record. Kerry met top Cambodian officials, including long-serving authoritarian Prime Minister Hun Sen, as well as members of the opposition and civic leaders, and discussed the possibility of a US-Cambodia trade and investment treaty. The opposition is led by a led by a politician and former finance minister, Sam Rainsy, who has been in self-imposed exile since November when he was expelled from the national assembly, stripped of parliamentary immunity and ordered arrested for an old conviction for defaming Cambodia's foreign minister. While praising Cambodia's economic strides, Kerry told reporters after his meetings that the US would like to see the country "as a thriving multiparty democracy," particularly as local and parliamentary elections approach next year and in 2018. "We care deeply about respect for human rights, universal freedoms, and good governance," he said. "Progress in each of these areas is really critical to being able to fulfill the potential of our bilateral relations but also the full potential of the aspirations of the Cambodian people." "Democratic governments have a responsibility to ensure that all elected representatives are free to perform their responsibilities without fear of attack or arrest," he said in a pointed reference to Sam Rainsy. "That is a fundamental responsibility of a democratic government. So as Cambodians prepare for elections next year and in 2018, it is important to allow vigorous but peaceful debate." The case against Rainsy, along with other attacks on the opposition, have brought an end to a political truce Hun Sen reached with the opposition in 2014 to end a parliamentary boycott. The opposition had accused Hun Sen's party of stealing the 2013 general election. After meeting Kerry, Cambodian Foreign Minister Hor Namhong said the top US diplomat had expressed concern about the state of the opposition but downplayed its seriousness. "He said that he is worried about the situation of the opposition in Cambodia. That is all, he said," Hor Namhong said. The US is one of Cambodia's main trade partners and it exports large amounts of textiles and shoes to the American market. Hor Namhong said he had asked Kerry to include clothing and footware in a group of duty free export items. As a US Senator, Kerry was instrumental in negotiating an agreement between the United Nations and the Cambodian government for a special tribunal to try the leadership of the Khmer Rouge, the ultra-communist group held responsible for the deaths of 1.7 million Cambodians while it held power from 1975-79. Cambodia is Kerry's second-to-go-last stop on an around-the-world diplomatic trip that began in Switzerland and took him to Saudi Arabia and Laos. He will visit China before returning home. His stops in Laos and Cambodia come ahead of a summit of Southeast Asian leaders that President Barack Obama is hosting in California next month.