UK oilfield services provider Petrofac reported a half-yearly loss on Thursday, pressured by subdued activity at its largest unit - engineering & construction (E&C).

The company posted an operating loss of $122 million for its E&C division, which has struggled with cost overruns amid contractual and commercial issues.

In June, Petrofac said it expected the unit, which accounts for half of the firm's revenue, to post a 20% operating loss on revenue of $500 million in the first half.

"Focus is on continuing to close out the legacy portfolio, improving our financial resilience and strengthening the balance sheet through the commercial settlements and advance payments due in the period," CEO Tareq Kawash said in a statement.

The Jersey-based company, which makes more than half of its revenue from UK, Thailand, Algeria and Oman, said order backlog stood at $6.6 billion as of June 30, up from $3.4 billion six months ago, and retained its forecast to be cash flow neutral by the year-end.

Petrofac reported an operating loss of $103 million for the half year ended June 30, compared to a restated profit of $77 million in the year-earlier period. (Reporting by Prerna Bedi in Bengaluru; Editing by Subhranshu Sahu)