(ShareCast News) - Cable & Wireless swung to a pre-tax loss in the first half on the back of costs related to its acquisition of Columbus Communications.For the six months ended 30 September, the telecommunications company posted a pre-tax loss of $1m (£650,000), compared with a profit of $132m in the same period a year ago.Still, revenue rose 4% to £1.18bn thanks to an "excellent" performance in the Caribbean, which is the group's largest region and where core earnings rose 22%.Group earnings before interest, tax, depreciation and amortisation increased 4% to $427m.The company said it now expects cost synergies of $125m from its acquisition of Columbus, up from a previous estimate of $85m.C&W did not declare an interim dividend, pointing to ongoing discussions with Liberty Global regarding a possible shares and cash offer for the company. However, it said it will declare an interim dividend of 1.33 cents per share if discussions with Liberty are not fruitful.Chief executive Phil Bentley said: "Our company has significant growth and synergy potential. Whilst we are in the first phase of our 3 year plan, we are pleased with initial progress and expect to deliver a strong second half and full year performance in line with outlook."We remain on track with our 3 year plan and are confident our business model will deliver significant long-term shareholder value creation."At 1055 GMT, C&W shares were up 0.5% at 74.45p.