SINGAPORE (Reuters) - Neptune Orient Lines (NOL) has said that it was in preliminary talks with CMA CGM SA and A.P. Moeller-Maersk on a potential acquisition of the Singapore-based container liner.

NOL, controlled by Singapore's state investor Temasek Holdings, has been struggling in a prolonged downturn in the global shipping market. It has posted four years of consecutive losses.

Earlier this year, NOL sold off its logistics business for $1.2 billion to Japanese freight carrier Kintetsu World Express Inc, and has been said to be looking to selling the rest of the company ever since.

"NOL has a duty to assess all options to maximise shareholder value and improve its competitiveness," the company said in a statement on Saturday.

"From time to time, NOL enters into discussions on possible combinations involving NOL, while remaining focused on returning its core liner business to sustainable growth and profitability."

Share prices in NOL, which has a market capitalisation of $1.9 billion, have risen 24 per cent so far this year. Its 12-month forward price-to-book value ratio stood at 0.81, compared with 0.99 of its peers, indicating the stock is undervalued, according to Thomson Reuters data.