* FTSEurofirst up 0.3 pct after choppy session
* Index down 0.9 pct on the week
* Athens' ATG remains close to 3-year lows
* Europe bourses in 2015: link.reuters.com/pap87v
* Asset performance in 2015: link.reuters.com/gap87v
By Sudip Kar-Gupta
LONDON, June 19 (Reuters) - European shares gained ground on Friday, helped by a rise in French telecom stocks and at steelmaker Thyssenkrupp, although concern over Greece kept a lid on the progress.
But main indexes trimmed gains in late trade as U.S. stocks reversed some of the previous day's sharp advances and the expiry of June stock options added to market volatility.
The pan-European FTSEurofirst 300 index closed 0.3 percent higher at 1,529.65 points, leaving it down 0.9 percent on the week.
French telecoms group Numericable rose 3.8 percent, lifted by an upbeat note from broker Kepler, while Orange progressed 0.9 percent after France announced a mobile spectrum sale.
Thyssenkrupp advanced 2.4 percent after Citigroup upgraded its rating on the stock to "buy" from "neutral".
Nevertheless, some traders remained cautious because of the deadlock between Greece and its creditors.
Euro zone leaders will hold an emergency summit on Monday to try to avert a Greek default after bank withdrawals accelerated and government revenue slumped as the Greek debt talks drag on.
Athens' benchmark ATG index advanced 0.7 percent but was still close to a near three-year lows reached earlier in the week, with the ATG down 17 percent so far in 2015, underperforming a 13 percent rise on the FTSEurofirst.
Richard Griffiths, associate director at Berkeley Futures, said the uncertainty over Greece meant he would avoid betting on short-term future gains.
"We're really only up on the back of the strength in the U.S., but I'd still be inclined to sell the rallies because of the Greek situation. It would be a brave man who goes in 'long' into the weekend," said Griffiths.
Aggressive stimulus measures from the European Central Bank have cushioned the blows to European financial markets from the problems with Greece, enabling some investors to maintain a positive attitude in spite of the worries over Athens.
"There is always opportunity in crisis. You may have to weather a little short-term pain should the worst case ensue, but ultimately you will be rewarded," said Gary Paulin, co-founder of brokerage Aviate Global.
Today's European research round-up (Editing by Robin Pomeroy)