* Southern border crossing is country's supply gateway
* Food, goods trucked in from Uganda, Kenya, Ethiopia
* Pasta, tea and sugar still comes from old foe Sudan
* Expats bring thousands of dollars daily via airport
By Ulf Laessing
NIMULE, South Sudan, Aug 30 (Reuters) - Almost two weeks after truck driver George Wala loaded building materials in the Kenyan port of Mombasa bound for a company in South Sudan he still hadn't reached his destination.
"I've been waiting for two days to clear my goods but no customs official has had time for me yet," the 30-year old Kenyan said, standing next to his truck in the muddy border post of Nimule, South Sudan's southern gateway to Uganda.
Every day up to 130 trucks from Uganda, Kenya, Ethiopia or even farther away arrive at the customs clearing area the size of a football field in the small border town.
Once a sleepy outpost built by colonial ruler Britain to mark its southernmost presence in Sudan, Nimule has become an economic lifeline for South Sudan since the world's newest state seceded from Khartoum in 2011 following decades of civil war.
Landlocked South Sudan depends on its oil exports flowing north to fund its state budget, and remains vulnerable to shutdowns caused by disputes over pipeline fees and border conflicts with its former enemy Sudan.
With almost no industrial production and just some 300 km (190 miles) of paved roads, the new nation depends on truck drivers like Wala to provide it with everything from diesel to beer, condoms, trousers, laptops and frozen salami.
Whenever the road is blocked, supermarkets across the country struggle to get supplies - tomatoes were hard to find in the capital Juba this week after floods cut off the Nimule border crossing for days.
Cross-border traffic has, however, been on the rise since a U.S.-funded project converted the dirt track from the British era into South Sudan's only paved road.
The economic impact was immediate. "The new Nimule road has boosted trade and also lowered the transport cost of goods," said Kimo Adiebo, professor of economics at Juba University.
Annual inflation has fallen to less than 10 percent from over 40 percent since the road was completed last autumn.
From Juba 205 km (128 miles) north of Nimule, some goods continue their trip on bumpy roads to the rest of a nation the size of France. It takes up to a month for soft drink cans from Dubai, loaded in Mombasa, to reach the countryside.
The Nimule border officials say they handle customs formalities quickly but truckers waiting in the scorching heat tell a different story. As with other state institutions, South Sudan has struggled to build up an effective customs service.
"They don't have inspection sheds like at the Kenyan-Ugandan border," said Wala, drawing nods from other drivers. "Here you need to wait for a customs official to come to your vehicle."
And the border is open only from 8 a.m. to 4 p.m. as the road from Nimule to Juba becomes dangerous at night with frequent accidents and bandits robbing passengers.
Still scarred from its long civil war, South Sudan has almost no significant food production apart from basic items such as milk, mineral water and beer - the latter thanks to a brewery built by SABMiller, one of the biggest foreign investments since independence.
The government has passed an investment act to encourage agricultural developments, but inefficient courts and non-existent land laws may deter even the most daring investors.
You can still get anything in Juba, a sprawling city of one-storey colonial era-houses, a few new modern office blocks and rows of container-type accommodation. Shops sell generators, television flat screens, baby milk and underwear from China.
Such goods arrive thanks to traders like Ashraf, who doesn't give his full name because part of what he does is not legal. Before he talks he beckons the reporter to the back of his computer shop, packed to the roof with the latest items.
He needs to buy dollars on the black market as the central bank struggles to provide them following a 16-month shutdown of South Sudan's oil output caused by the disputes with Sudan.
As important as dollars are connections. "If you don't know any customs officer they will charge you too much," he said.
To secure steady supplies and low duties he or a colleague travels to Kampala or Mombasa almost every month to stock up and ship the computers in a container truck, costing $8,500.
To make sure his goods arrive in time he clears the goods himself in Nimule. Even if he secures a low customs duty, laptops still cost $300 more than the same model in Uganda.
Until independence much of South Sudan's needs came from the north, with imports arriving in Port Sudan on the Red Sea and then travelling up the Nile. Since a 2005 peace pact ended the civil war, southern officials have sought to lower dependency on Khartoum by planning new roads to Uganda, Kenya and Ethiopia.
Several road projects are in the works but for years Nimule will remain the only all-weather overland transport lifeline.
In the run-up to secession, Sudan closed the joint border in what South Sudan officials called an economic war. Both sides agreed in March to reopen it but this has not happened yet due to mutual mistrust.
Still, some products slip over to the South.
"The pasta comes from Sudan, the tea and the sugar," said Mohamed Adam, one of thousands of Sudanese working as food retailers in South Sudan. "The rest comes via Uganda and Kenya."
Despite the huge import bill, South Sudan's pound has stayed relatively stable. It lost 35 percent after the oil shutdown in early 2012 but has traded since on the black market at between 4 and 4.6 to the dollar versus an official rate of around 3.
In contrast, the Sudanese pound lost 75 percent on the black market due to the loss of pipeline fees from South Sudan
Diplomats attribute the South Sudan pound's resilience to an army of aid workers and U.N. officials in the country as well as foreign entrepreneurs such as builders or restaurant owners. With credit cards not working and bank transfers almost impossible expats bring in thousands of dollars daily through Juba airport.