* PetroChina and Yangon near deal on crude supplies
* Pipeline to supply new refinery in China's Yunnan
* Tanker with crude for pipeline to arrive this week
* Long-delayed project tests China-Myanmar relations
By Yimou Lee, Chen Aizhu and Shwe Yee Saw Myint
YANGON/BEIJING, March 21 (Reuters) - Nearly a decade in the making, a project to pump oil 770 km (480 miles) across Myanmar to southwest China is set for imminent start-up, with a supertanker nearing the port of Kyauk Phyu, marking the opening of a new oil trading route.
Dogged by sensitive relations between Naypyitaw and Beijing, the $1.5 billion oil pipeline has been sitting empty for two years, but the two sides are now close to a deal, said Myanmar-based government and industry sources, despite some last-minute tensions.
An agreement between China's PetroChina and Myanmar's government will allow the state energy giant to import overseas oil via the Bay of Bengal and pump it through the pipeline to supply a new 260,000-barrels-per-day (bpd) refinery in landlocked Yunnan province.
The new oil gateway fits with China's "One Belt, One Road" ambitions, linking it with central Asia and Europe, and will provide a more direct alternative route to sending Middle Eastern oil via the crowded Malacca Straits and Singapore.
It would also be a rare win for China in Myanmar after a diplomatic offensive aimed at forging better ties with its resource-rich neighbour, which has often been wary of Beijing's economic clout.
Aung Myat Soe, deputy director of planning under the state-owned Myanmar Oil and Gas Enterprise (MOGE), said the project was awaiting a final sign-off by the Minister of Electricity and Energy.
Major issues including transport tariffs and Myanmar's tax take on the oil have been settled, but port fees have yet to be finalised, said a Myanmar-based industry source familiar with the matter.
"The two sides are working to finalize the terms and sign the contract," the person said, declining to be named as the information is not public.
"I can't say for sure when the deal would be sealed - it could be in a couple of days or early April."
The pipeline will have an eventual capacity of 400,000 bpd, about 5 percent of China's daily import demand, but the start-up of the Yunnan refinery has been held up as PetroChina and Myanmar negotiated final terms for delivering the oil.
PetroChina plans to start test production at the refinery in June, aiming to expand its foothold in China's fuel-short southwest which has so far relied largely on rival Sinopec for supplies, said two Beijing-based oil officials familiar with the Yunnan refinery.
Before then, PetroChina is expected to purchase another 7 million barrels of crude for the pipeline, to stock up fuel for about one month's production at its new refinery, said one of the officials.
While the deal is still to be finalised, oil is already on its way to supply the pipeline, straining relations with Myanmar.
Shipping data in Thomson Reuters Eikon shows the oil tanker United Dynamic, carrying one million barrels of Azeri crude, is currently off the coast of southern India and expected to unload its cargo at Kyauk Phyu this week.
A Myanmar government official said there had been "a big argument with the Chinese" over the move to ship in crude before the contract was finalised, while a second official said the entry of the tanker was pending approval from Myanmar's navy.
PetroChina did not respond to requests for comment.
Any delay would be costly for the oil shipper, which is carrying crude worth over $50 million and which has a daily tanker charter cost of nearly $20,000, excluding fuel and crew costs.
The deal is also controversial in China as it has been tainted by a graft probe into PetroChina's ex-chairman Jiang Jiemin, a supporter of the project.
Critics have raised conerns about the economic viability of the project, which also includes a natural gas pipeline, which was touted as providing "strategic new channels" for China's energy needs.
At the same time, the prolonged squabbling over key features of the deal, first discussed back in 2004, has soured Chinese enthusiasm for the project.
"There are open questions about the economics and future cooperation with Myanmar, given the repeated delays and under-utilization," noted a senior PetroChina official who requested anonymity as he's not authorized to speak to press.
Reporting by Yimou Lee in YANGON, Chen Aizhu in BEIJING and Shwe Yee Saw Myint in NAYPYITAW; Editing by Henning Gloystein and Richard Pullin