US diplomatic cables unveiled by WikiLeaks have exposed backstage manoeuvres surrounding a UN investigation into the murder of Lebanese ex-premier Rafiq Al-Hariri, stoking new controversy around the probe.

The cables, which are among some 4,000 more secret documents on Lebanon expected to be released by the whistleblower website or its affiliates, reveal UN frustrations with both Syria and France over their level of cooperation with the probe.

They also detail repeated appeals from investigators for US assistance and show their deep concern over the detention, without charge for four years, of four high-ranking Lebanese security officials in connection with Hariri's 2005 assassination.

The new WikiLeaks revelations come as the Special Tribunal for Lebanon (STL), tasked with investigating the massive Beirut bombing that killed Hariri and 22 others, is reportedly poised to indict members of Hezbollah in connection with the murder.

The powerful Shia resistance group, which fought a devastating 2006 war with Israel, has warned any such accusation would have grave repercussions in Lebanon.

According to a series of cables obtained by WikiLeaks and published by Lebanese daily Al-Akhbar on its website, STL prosecutor Daniel Bellemare last year complained to then US ambassador Michele Sison that Syria, initially accused of Hariri's murder, was treating his investigators as "school kids in short pants."

"They provide us with 40,000 pages in Arabic. After we translate them and find nothing of interest, they feign surprise and hand us another 40,000 pages," read a cable dated 27 January 2009.

According to another cable published by the English-language Daily Star newspaper, Bellemare's predecessor, Serge Brammertz, complained in 2006 to then US ambassador Jeffrey Feltman, now a deputy secretary of state, that France was withholding its cooperation from the investigation.

Brammertz is quoted as saying that even Syria had been more cooperative than some EU countries.

Both Brammertz and Bellemare voiced concern that the detention of the four Lebanese generals, who were released last year, violated international law.

Bellemare acknowledged that the timing of their release was sensitive and could bolster Hezbollah and its allies in the run-up to last year's parliamentary election in Lebanon.

Another leaked cable detailing a request from Bellemare for additional assistance from the United States -- already a major donor to the STL -- made headlines in the Lebanese press.

The prosecutor is quoted as asking Sison for information on Syria and, in a separate cable, requesting that the United States loan his inquiry two analysts whose salaries, along with others, would be paid for by the US Federal Bureau of Investigation.

"Bellemare showed a good understanding of the problems associated with complying ... but his frustration was nonetheless evident: 'You are the key player. If the US doesn't help me, who will?'," read the cable, dated October 2008.

Hezbollah has said the leaks are further proof the United States is manipulating the probe.

"The information leaked on meetings between the prosecutor and the (then) US ambassador confirms what we have always said -- that the US administration is using the court and the investigation committee as a tool to target the resistance," Hezbollah MP Hassan Fadlallah told AFP.

Another cable published by the Daily Star quotes a top security official as saying he believed Hezbollah operative Abdul Majid Ghamloush was linked to Hariri's murder and two subsequent political assassinations.

One figure who features prominently in the US embassy cables is Walid Jumblatt, head of Lebanon's minority Druze community.

"Jumblatt warned that, despite recent progress with the Special Tribunal, Syria would not change its behaviour until the Assad regime truly feels threatened," read a cable dated 21 February 2008, referring to Syrian President Bashar al-Assad.

Jumblatt, once a vociferous critic of Damascus, last year pulled a political volte-face by quitting the pro-Western coalition he helped create in order to move closer to the Hezbollah-led camp supported by Syria and Iran.

His only reaction to the leaks was to say his current position was "real, natural and historic" and to suggest a return to "pigeon carriers or mail on horseback," saying it was "safer".