PHNOM PENH (THE PHNOM PENH POST/ASIA NEWS NETWORK) - Its president imprisoned on a charge of treason and its existence under threat, the Cambodia National Rescue Party last week renewed its calls for the international community to step in and stop what's widely seen as an all out assault on the Kingdom's democracy.

But with China throwing its support behind the premier Hun Sen, the West's statements of condemnation and concern, which have flooded in from embassies, NGOs and the United Nations in recent days, will have little impact, particularly in the absence of concrete measures, analysts said.

Building on a statement of support from China's Foreign Ministry, senior Chinese diplomat Wang Jiarui met on Thursday with National Assembly President Heng Samrin to offer private assurances amid the mounting criticism, according to Samrin's spokesman Sorn Sarana.

Jiarui, the former head of the Chinese Communist Party's international liaison department and current vice chairman of the National Committee of the Chinese People's Political Consultative Conference (CPPCC), reaffirmed Beijing's support following the late-night arrest of CNRP President Kem Sokha, Sarana said. He said the official, whose committee is described as a non-state organ that advises on state affairs, expressed the sentiment that "an obstacle for Cambodia is also an obstacle for China".

"China is behind Cambodia to help and support," he said, relating the discussion. "The success of Cambodia is also the success of China."

A representative from the Chinese Embassy in Phnom Penh did not respond to messages to verify Sarana's characterisation of the discussion, but for analysts, China's backing was hardly surprising given Hun Sen's long drift into Beijing's orbit.

Backed by more than US$one billion (S$1.34 billion) in foreign direct investment and US$265 million in overseas development aid, according to 2016 figures, Chinese support insulates the premier from external pressure, at least to a certain extent, analysts said.

Carl Thayer, a Southeast Asia expert at Australia's University of New South Wales, said China had previously shown its willingness to supply military equipment and plug holes left by the withdrawal of Western aid. Cambodia, meanwhile, has repeatedly backed China's position on the contested South China Sea.

"China will pick up the pieces if the US or other donor countries resort to sanctions or other punitive actions against Cambodia," Thayer said, adding that nonetheless, the support was not a carte blanche endorsement of Hun Sen, who has ruled Cambodia for more than three decades.

"The message was subtle but clear. China will support Hun Sen under these conditions, but if Hun Sen cannot protect Chinese interests they will support a CPP leader who can."

The premier himself has shown no signs he's willing to cede power should his ruling Cambodian People's Power lose next year's election, announcing on Wednesday that he planned to rule for 10 more years.

Eleven months out from the crucial national ballot, the government has pursued what's widely seen as a relentless crackdown against the opposition, independent media and civil society, culminating this week with the arrest of Sokha, who faces up to 30 years in prison on a "treason" charge for what officials say is a US-backed plot to topple the government.

A well-connected observer familiar with thinking inside the CPP said the government's virulent anti-Americanism reflected a belief that the US and US-backed organisations were supporting the CNRP, as well as frustration over Washington's reluctance to forgive war-era debt. Nevertheless, the observer, who requested anonymity because of the tense political environment, said the escalation against the US was a gamble.

He described anxiety in the CPP about the US's recent announcement of visa restrictions for Cambodians, which came in response to Cambodia's refusal to accept deportees as part of a controversial US programme to sends home long-term non-native residents who are convicted of a felony.

The possibility of trade restrictions also worried many in the party, he said. The scrapping the EU's "anything but arms" preferential trade arrangement, or the US's zero tariffs for travel wares could have "devastating" economic consequences given European and American markets are vital to Cambodia's almost US$7 billion garment export sector.

With the minimum wage rise in Cambodia making other countries in the region more appealing to manufacturers, lead Asean analyst for the Economist Intelligence Unit Miguel Chanco said such moves would be a stronger tool than aid cuts, which have long been threatened but without much impact.

However, in light of North Korea's nuclear ambitions and the Myanmar military's crackdown against ethnic Rohingya in Rakhine state - and considering the political upheaval in the US and EU - discussions of such actions were "unlikely" to feature high on the agenda, he said.

"Simply put, the EU and the US have bigger domestic fish to fry. The former is dealing with the complexity of Brexit, while the latter is busy dithering on Donald Trump's controversial domestic agenda," Chanco said.

According to a government database, China last year provided about 30 per cent of Cambodia's US$one billion overseas development aid budget, followed by Japan, which contributed 10 per cent, and is also second only to China for foreign direct investment.

Following Sokha's arrest, the Japanese Embassy released a cautious statement calling on the ruling and opposition parties to "make efforts to create a suitable environment to realise a free and fair" election.

Deputy Asia Director of Human Rights Watch Phil Robertson urged Japan not to "soft-pedal", and to use its central role at the UN Human Rights Council to take a strong position against threats to the legitimacy of next year's election, noting Tokyo was a major supporter of preparations for the upcoming ballot and had led the UNTAC mission that staged Cambodia's 1993 vote.

"I would take five statements of concern, and if I got something from Japan that was somewhat terse and tight and strong, I would match those up against the others," Robertson said, noting Japan's preference for closed-door diplomacy.

"Japanese critical statements are sort of like unicorns; you get a critical Japanese statement, it's like, 'Did I just see a magical creature?'"

A small glimpse of Japan's behind-the-scenes courting of Cambodia emerged last month, when Hun Sen posted a video of a surprise birthday party organised in Tokyo by Prime Minister Shinzo Abe, complete with a personal rendition of "Happy Birthday" and a new set of golf clubs.

Paul Chambers, a Southeast Asia expert at Thailand's Naresuan University, said Japan's "jousting" with rival China would likely temper the strength of any public response, and the potential of punitive action.

"If Japan were to walk away from Cambodia, Tokyo would provide a vacuum which Beijing would only be too willing to fill," Chambers said.

Noting Toyko had "little appetite for confrontation", associate professor of diplomacy and world affairs at Occidental College, Los Angeles Ear Sophal said he saw little hope for anything "dramatic and coordinated" from the international community.

"The last time anything serious happened in terms of aid suspension [1997], 100-200 people died," he said, referring to the violent factional fighting in which Hun Sen ousted his royalist rivals from a coalition government.

"And, indeed," he added, "China has already made a statement endorsing Cambodia's actions."