NAIROBI, Kenya — South Sudan is building up an armory of tanks and heavy weapons, according diplomatic cables released by WikiLeaks, and in the North, the Khartoum government is stocking an even more formidable pile of armaments.

Despite a peace agreement between the two sides and a looming January vote on their official separation, the weapons buildup is a worrying indication that neither side is particularly committed to peace and that both are, in fact, preparing for war.

The cables revealed that South Sudan was buying heavy weapons in 2008. Thirty-three tanks and other munitions destined for South Sudan were aboard a ship, the MV Faina, when it was hijacked by Somali pirates. At the time, the Kenyan government said the arms were headed for Kenya, but the leaked documents show that the arms were in fact going to South Sudan.

“It is a poorly kept secret that the tanks are bound for the Government of Southern Sudan,” wrote U.S. Ambassador Michael Ranneberger in an October 2008 cable, four months before the 10,000-ton cargo ship was released in exchange for a $3 million ransom.

The cable, revealed on the WikiLeaks website this week, casts light on an illicit arms race underway ahead of a referendum due on Jan. 9 in which southern Sudanese are widely expected to vote for separation from the north in order to become independent from the Khartoum government.

A 2005 peace agreement ended the North-South civil war but mistrust and animosity continue to define relations between the mostly black Christians in the South and the predominately Arab Muslims in the North.

As international concern grows that the partition of this huge, oil-rich country may spark a return to war, it seems that both sides are preparing for just such an outcome despite arms embargoes imposed by the United Nations, the European Union and the peace agreement itself.

“Since the [peace agreement] we have seen both the North and South investing serious amounts of money in armaments and military equipment,” said Claire MacEvoy, project manager at the Small Arms Survey, a Geneva-based organization that tracks weapons flows into and within Sudan.

MacEvoy said that despite the attention the hijacking of the Faina brought to southern arms stockpiling, Khartoum remains a “formidable enemy” and had spent far more money to buy much more sophisticated equipment.

In the diplomatic cable, Ranneberger said that since 2007, “Kenya’s Ministry of Defense has indeed played a major role in assisting the Government of South Sudan to receive arms shipments from the Government of Ukraine.”

Researchers said that the Faina was the third arms shipment from Ukraine via Kenya in two years. Southern Sudan is a landlocked region so armaments are shipped to the port of Mombassa and then transported by rail and road to neighboring southern Sudan.

According to the Small Arms Survey, the Faina’s military cargo included 33 T-72M1 battle tanks as well as thousands of rounds of anti-tank and fragmentation rounds, six truck-mounted 122mm BM-21 multiple rocket launchers, six 14.5mm anti-aircraft guns and 36 shoulder-fired rocket-propelled grenade launchers.

Since the cargo was released in February 2009, the tanks are thought to be held at the Kenyan army’s Kahawa barracks close to Nairobi. The first and second shipments consisting of anti-aircraft guns, rocket and grenade launchers, assault rifles, tanks, spare parts and ammunition are believed to have reached their destination in southern Sudan.

Before the Faina was hijacked, the Sudan People’s Liberation Movement (SPLM) government had already bought 77 tanks, more than a dozen anti-aircraft guns, hundreds of RPGs and tens of thousands of AK47s.

More recently reports have revealed that the southern army, known as the Sudan People’s Liberation Army (SPLA), has bought at least 10 Russian Mi-17 helicopters. They are multipurpose aircraft commonly used for transporting troops or equipment but can be converted into gunships.

Over the four years between 2006 and 2009, the southern government’s own figures show that it spent on average 30 percent of its entire budget each year on the military, roughly $2.5 billion. Added to this minimum figure is an unknown amount of off-budget spending.

All these purchases still leave the south vastly outgunned and outnumbered by the North. President Omar al-Bashir’s administration in Khartoum has bought substantial armaments, including dozens of ground attack aircraft, armored personnel carriers and tanks, mostly from China and Iran.

The Small Arms Survey estimates that South Sudan's SPLA troop numbers at 125,000 while the North's Sudan Armed Forces (SAF) is estimated to be 225,000 strong.

Juba’s fixation on anti-aircraft weapons and helicopters is due to the north’s air superiority and long history of using deadly and indiscriminate Antonov bombing raids during the civil war with the south as well as in Darfur more recently.

For its part the SPLA has never before had the capacity to foil aerial raids. MacEvoy described the south’s lack of air capacity as “the SPLA’s weakest point.”

In recent years the SPLA has publicly declared its intention to build up an air force, considered part of its ongoing efforts to ‘professionalize’ the former rebels. U.S. companies DynCorp and PAE are among the contractors training the SPLA into a professional army. Southern officials say that the purchases of new weapons is also part of their bid to form a modern armed force capable of defending the emerging nation.

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