* Frosts too hard for Ukrainian grain crops
* Cold snap sustained in Russia's south
* Ukraine has snow layer on 60 pct of land
* AgMin mulls wheat export limits
* Russia's Novorossiisk confirms loading resumed (Adds Russian crop weather, Novorossiisk loadings resumed)
By Pavel Polityuk
KIEV, Feb 9 A fierce cold spell has killed most of the winter barley and winter rapeseed crops and seriously damaged wheat in Ukraine's eastern and southern regions, while threatening winter crops and slowing exports in Russia.
"We have written them off," Tetyana Adamenko, head of the agricultural department of Ukraine's meteorological service, told Reuters, referring to barley and rapeseed winter crops.
In Ukraine and parts of Russia's south, crops lacked a deep enough layer of snow to protect them from temperatures of about minus 25 Celsius (-13 Fahrenheit).
Russia's state forecaster, the Hydrometeorological Centre, said on Thursday Russia's south would continue to face extreme frosts in the coming days, with temperatures 12 to 17 degrees Celsius below multi-year averages.
The forecaster has been cautious about the impact of the cold on Russia's crops, and analysts say winterkill could turn out to be no greater than average when official statistics are released at the end of the month.
But in Ukraine, several days of record lows have been enough to kill most crops in eastern and southern regions, which were already weakened by drought during sowing, Adamenko said.
"The situation across Ukraine is very varied: we have enough snow on 60 percent of our land in the central and northern parts, while a lack of snow has hit the east and south," Adamenko said.
Adamenko said last week that Ukraine's harvest of winter grains could fall by 42-58 percent to between 10 million and 14 million tonnes due to poor weather during sowing and wintering.
Ukrainian agriculture officials and analysts say about 20 percent of winter grains have not come up because of drought during sowing, while 33 percent of those that had sprouted were in a poor state.
The Farm Ministry said at least 2 million hectares of damaged winter crops would be reseeded this spring mostly with barley and maize.
Adamenko said Ukraine might lose 40 percent of the sown area. Ukraine sowed 8.4 million hectares for the 2012 winter grain harvest, including 6.7 million hectares of winter wheat, 1.4 million of winter barley.
Ukrainian analysts have, by contrast, forecast losses of about 8 percent in Russia, in line with multi-year averages, although the harsh frosts in Russia's key southern exporting regions, if sustained, could cast doubt on next year's exports.
Russia is expected to reap 45.5 million tonnes from 16.4 million hectares sown to winter grains, SovEcon has forecast.
Both countries have broached the possibility of new export restrictions this year to preserve domestic supplies but have so far abstained from imposing limits.
Ukrainian agriculture officials have said they would avoid restrictions even if this year's wheat harvest shrinks, but traders say a small wheat crop could force the Farm Ministry to intervene in the market.
"They are worried about wheat and they are thinking what the policy should be," a large Ukrainian trader said.
"The idea is to sign a document with traders in which they would limit wheat exports".
Another trader said the exports of wheat could be limited to 1.2 million tonnes in February and March.
"It's enough for us. The exports of wheat will not exceed 500,000 tonnes in February, and 700,000 tonnes in March seem a real figure," trader said.
The ministry declined to comment.
Even without curbs, current exports from the two Black Sea powerhouses are already falling short of expectations due to cold, stormy weather, which has hampered loading in their key ports.
UkrAgroConsult agriculture consultancy said Ukrainian grain exports might total 1.3 million tonnes in January but could fall to 1.0 million in February because of icy weather hitting the ports. Russia loaded 1.4 million tonnes in January, slightly short of expectations, SovEcon consultancy said last week.
In Russia, Novorossiisk Commercial Sea Port confirmed loading had resumed at its grain terminal on Wednesday after being suspended for the second time in a week, though conditions were difficult and loading of crude oil was stopped.
Shallow water ports on the Azov Sea, which can handle over a million tonnes of grain during peak months, remained iced over.
But UkrAgroConsult said a fall in the 2012 wheat harvest would not remove Ukraine from the lucrative export market and the country was likely to export 6.3 million tonnes of wheat in the 2012/13 season.
Ukraine, which consumes 12 million tonnes of wheat per season, harvested 22.3 million tonnes of wheat in 2011 and exported no more than 3.0 million tonnes of wheat so far this season.
"With this pace of exports, we could have enough wheat for local needs and for exports even in conditions of a critical fall-off in the harvest", a trader said. (Reporting by Pavel Polityuk and Melissa Akin; Editing by Richard Balmforth and Jane Baird)