Ukraine has warned of a deeper-than-expected drop in its wheat harvest this year, signalling that winterkill may have wrought worse damage to the Black Sea grain powerhouse.

With last year's crop pegged at 20.9 million tonnes, the forecast implies a 2010 harvest of well below 18 million tonnes, taking it significantly beneath external forecasts.

UkrAgroConsult, the Kiev-based analysis group, has pegged the crop at 18.86 million tonnes, with the USDA forecasting a 19.5million-tonne harvest.

Viktor Slauta, the Ukrainian deputy prime minister, said the country's wheat production may be 15% lower than in 2009, citing large losses in winter wheat crops.

While many crops were protected from cold damage by snow, others, notably in northern areas, were held in an ice crust for more than two months.

A USDA report earlier this week said that "various forecasts over the past two months have estimated winterkill at anywhere from 3-30%", although the bulk of the losses have been attributed to barley and rapeseed, which are more susceptible to cold.

However, some analysts have warned that, with autumn-sown crops planted in dry conditions, some wheat may have headed into the winter in a weaker-than-normal state.

Furthermore, many farmers have taken to sowing winter crops late, to narrow the window before winter in which they are susceptible to insect pests and disease, and so enable savings on pesticide bills.

"Later planting offers the advantage of a reduction in the use of insecticides and fungicides, but also raises the risk of weather-related damage in the event of an early winter," the USDA briefing said.