JOHANNESBURG (Reuters) -South African retailer Pick n Pay said on Wednesday it expects to swing to an annual headline loss of up to 281.13 cents per share as the poor performance of its core supermarkets business weighed on the group.

Pick n Pay, which also owns discount grocery retailer Boxer, said it expects to report a comparable headline loss of between 228.31 cents to 281.13 cents in the year ended on Feb. 25, from headline earnings per share (HEPS) of 264.12 cents in the previous year.

The retailer also flagged a 2.8 billion rand ($155 million) non-cash asset impairment of its core Pick n Pay supermarkets stores. The impairment does not affect HEPS, but affects earnings per share, which will swing to an earnings loss of up to 686.01 cents.

A writedown of 1.8 billion rand is for selected loss-making company-owned Pick n Pay stores, "which will be closed or converted to Pick n Pay franchises or Boxer stores under the group's strategic plan," it said.

And a 1 billion rand impairment of assets is for underperforming company-owned stores that will remain open, the retailer added.

When it reports its results next Monday, the retailer expects to have increased group sales by 5.4%, boosted by Boxer and its clothing stores. Pick ffn Pay South Africa sales, however, are seen inching down by 0.2%.

($1 = 18.0715 rand)

(Reporting by Nqobile Dludla, Editing by Louise Heavens)