SYDNEY - Caltex Australia Ltd, the nation's only listed refiner, flagged a weak outlook for the first half of 2010 on Wednesday and said it would close down a lubricant refinery, sending its shares down 5 percent.

Caltex, which was barred by Australian regulator from buying ExxonMobil Corp's Australian gas service stations, also said it expected full-year 2009 operating profit on replacement cost basis, including items, of A$180-205 million ($163-$186), compared with A$186 million last year.

Global refiner margins remained under pressure in the second half of 2009 because of depressed demand and the expected growth in global surplus refinery capacity, Caltex said in a statement.

Excluding items, Caltex expects full-year replacement cost basis profit of A$300-325 million.

Caltex shares were down 5.2 percent to A$8.54, outpacing a 0.8 percent fall in the benchmark S&P/ASX 200 index .AXJO.

Caltex said it would shut down a lubricating oil refinery in Sydney as the plant produces outmoded lubricant products. The closure will result in a one-off charge of A$170 million.

Caltex's refinery margins were also impacted by a higher Australian dollar and firmer crude oil prices. Refinery margins fell more than 71 percent in the second half to $2.60 a barrel.

Caltex said it was still considering what action it will take over the regulator's block last week on the purchase of the ExxonMobil service stations and was still in talks with the regulator.

Caltex said it will decide whether to pay a final dividend, depending on the outcome of those talks. ($1=1.105 Australian Dollar) (Reporting by Denny Thomas;)