(ShareCast News) - Defence group Ultra Electronics Holdings saw its interim pre-tax profit plunge on the back of a writedown due to the loss of its contract in Oman.In the six months to 30 June, the London-listed company posted a 67.6% year-on-year drop in pre-tax profits to £14.8m, while revenue declined 2.7% to £331.7m, as the group booked a one-off charge of £16.4m after the termination of its Oman Airport IT deal.The FTSE 250 company saw sluggish performance in its US and UK markets, with the value of its order book declining 13% to £762.1m, although group chief executive Rakesh Sharma said the results were in line with expectations."The uncertainty surrounding the next US fiscal budget and the potential of a continuing resolution in relation to Government appropriations has continued to dampen US defence revenues," he said."The full-year performance is weighted to the second half of the year and is expected to remain in line with previous guidance of a stable 2015 performance."The company said it will pay an interim dividend of 13.8 pence per share, a 4.5% increase year-on-year.Ultra Electronics shares were up 0.86% to 1,760.00p at 0857 BST on Monday.