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 Shiite militant 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 January 27, 2009.
A member of Al-Akhbar's editorial team told AFP that the paper had been hit by a cyber attack since publishing the leaked cables.
"We have been the victim of a cyber attack targeting the paper's internal information system for the past few days," Elie Chalhoub said, adding that Al-Akhbar's cooperation with WikiLeaks "may well be the principal reason for the attack."
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.
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 that 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 February 21, 2008, referring to Syrian President Bashar al-Assad.
The veteran Druze leader's only reaction to the leaks was to say his current position was "real, natural and historic", and to suggest a return to "carrier pigeons or mail on horseback," saying it was "safer".
------------------------------------------------------------------------------