Bids are being sought to buy Chevron's Pembroke refinery, the company has revealed this week.
Chevron has announced its intention to solicit bids for some of its operations in Europe as part of the company's global downstream restructuring.
A statement issued on Tuesday said: "This includes our company's Pembroke refinery, as well as fuels marketing, aviation and lubricants operations in Europe. Our European Oronite, Arteco, Base Oils and Marine Lubricants operations are not included."
The statement continued: "To confirm, this process is to determine interest in our operations in Europe. No decision has been made to sell any asset at this time.
And concluded: "We have no plans to idle any of our refineries. Our continuing focus is on operating Pembroke refinery in a safe, reliable and environmentally responsible manner."
The Pembroke refinery, one of the largest manufacturers in north-west Europe, can process 220,000 barrels of crude oil daily. It produces 17 different products, including petrol, diesel and kerosene.
The refinery was opened in 1964, and currently provides work for around 1,400 people.
The news has sparked concern amongst local politicians and civic leaders.
Local MP Nick Ainger was one of the first to express his concern about the uncertainty facing the refinery.
He said: "I have had talks with the refinery management and First Minister Carwyn Jones. This announcement follows the company's announcement in January that they were restructuring their global downstream operations.
"The company tell me that it is business as usual and their multi-million capital investment programme at Pembroke in 2010 and 2011 is going ahead. That is a vote of confidence in the plant's future.
"There are no plans to cut the workforce and the apprenticeship scheme continues. The investment programme will mean more jobs for local contractors. This plant is not being run down for closure.
"However, the very fact that the European operations are on the market will cause uncertainty for the workforce. Chevron pumps about £65million into the local economy and is by far the largest private sector employer in Pembrokeshire.
"First Minister Carwyn Jones understands how vital the refinery is to Pembrokeshire's economy and is committed to maintaining the plant.
"Refineries do get bought and sold and continue operating. The Murco refinery at Milford Haven has had four different owners in its less than 40-year life."
Leader of Pembrokeshire County Council, Clr. John Davies, was also worried.
"Obviously any speculation over the future of the refinery is unsettling for all concerned," he said.
"I have received an undertaking from Chevron that proposed investment at the refinery will continue and that they have no plans to idle the plant. That is reassuring given that the refinery is such an important asset to the Pembrokeshire economy."
Meanwhile, Labour AM for Mid and West Wales, Alun Davies, said: "We must remember over the years, significant investment has taken place at the Pembroke refinery, and that investment continues with support for apprentices.
"It will be a very worrying time for the 1,400 employees and their families who depend on these local jobs. However, we must remain confident that a buyer steps forward to continue operations here.
"I have already spoken with the First Minister Carwyn Jones to bring him up to date with the situation. I will be pressing the Welsh Assembly Government to do everything it can to work with the company, prospective buyers and our Government colleagues in Westminster to maintain the current level of local jobs which in turn supports the wider Pembrokeshire economy."
Welsh Labour leader and First Minister, Carwyn Jones, added: "As a government, we have already been in dialogue with Chevron seeking clarification about their medium and long term intentions.
"We have been assured there is no immediate threat to the Pembroke refinery - from either sale or closure. We will be doing all we can as a Government, to maintain this plant in the future."
The GMB, Britain's general union, will be seeking talks with all concerned to ensure that employment is safeguarded.
Jeff Beck, GMB regional officer, said: "This refinery is a huge employer in West Wales. It is essential that the UK and Welsh Governments ensure that whoever buys this will pledge to keep it open. We cannot have another Corus situation in West Wales."