UPDATE 1-Aramco, Shell to start clean diesel unit by year end

* Saudi Aramco-Shell starts commissioning of new unit

* Full operations at 90,000 bpd unit expected by end Dec

KHOBAR, Saudi Arabia, Nov 10 (Reuters) - Saudi Aramco is expected to bring online a new 90,000 barrels per day (bpd) clean diesel unit at its joint-venture refinery with Royal Dutch Shell (RDSa.L) by December, a company source said on Tuesday.

The new addition at the 305,000 bpd refinery is undergoing commissioning, the source said.

"The project was completed in October and the unit is under commissioning," the source said.

The new unit, has the potential to produce about 90,000 bpd of ultra-low-sulphur diesel, the source said.

"Operations would start in November, there might be some hiccups, so it (start-up) might drag to December," the source said but declined to offer more details.

Aramco said in July that the unit, which makes the refinery the kingdom's first producer that complies with new environmental standards would start up in October. [ID:nL1337711]