(Adds CEO comments, details)

LONDON, Aug 28 (Reuters) - Oil producer Gulf Keystone Petroleum GKP.L said a production increase at its flagship Shaikan oilfield in Iraqi Kurdistan may be delayed until next year due to a shortage of international staff following their evacuation because of escalating violence.

Gulf Keystone, one of the main oil producers in the resource-rich northern Iraqi region, said the return of around 44 evacuated staff was essential to meeting its year-end target of increasing output at Shaikan to 40,000 barrels equivalent per day (boepd), up from 20,000-25,000 boepd now.

"Certain consequences of the recent security situation, including the current short-term limited availability of some international contractors, may cause this to move to first quarter, 2015," it said in a first-half results statement.

The news dragged down Gulf Keystone's shares in London to trade 8 percent lower at 0746 GMT.

Chief Executive John Gerstenlauer told Reuters the British government's removal of a travel warning in the Arbil region and the restart of Western airline flights were necessary to allow international staff to return.

Apart from a small reduction in output for one day in early August, production from Shaikan has been unaffected by security tensions in the area.

Gulf Keystone also reported widening losses after tax of $29.8 million in the first half of the year, compared with a loss of $26.4 million in 2013.

The firm said it was owed $35 million in crude export sales, adding it was one of its priorities to establish a regular payment system for its Kurdish oil.

Gerstenlauer said discussions with the Kurdistan Regional Government on the subject were progressing well.

"If ongoing discussions with the Ministry of Natural Resources are successful, a 'catch-up' effect may occur in H2 substantially improving cash flow generation," said analysts at Deutsche Bank.

(Reporting by Karolin Schaps; Editing by Neil Maidment and David Evans) ((karolin.schaps@thomsonreuters.com)(+44 0207 542 6622)(Reuters Messaging: karolin.schaps.reuters.com@reuters.net))

Keywords: GULF KEYS PETR SHAIKAN/