Britain's FTSE rises as firmer oil stocks outweigh Greek concerns

* Rise in oil stocks prop up FTSE 100

* Citigroup (NYSE: C - news) downgrade weighs on Admiral

* Sage lifted by Investec (LSE: INVP.L - news) upgrade

By Sudip Kar-Gupta

LONDON, June 25 (Reuters) - A rise in major oil stocks propped up Britain's top equity index on Thursday, helping to offset pressure from persistent concerns over Greece's debt problems.

Britain's benchmark FTSE 100 equity index rose 0.3 percent to 6,863.70 points going into the middle of the trading session.

The FTSE 100 is some 4 percent below a record high of 7,122.74 points reached in April, as worries over Greece have knocked back European stock markets over the last month.

The FTSE - which has a greater exposure to energy and commodity stocks than rival European markets in Paris and Frankfurt - got some support from the oil sector on Thursday.

Crude oil prices advanced, which boosted the shares of energy groups BP and Royal Dutch Shell (Xetra: R6C1.DE - news) , with both BP and Shell (LSE: RDSB.L - news) rising around 1 percent.

"The oil stocks are giving it a good push up today, although I don't think we'll see much major progress until the Greek situation becomes clearer," said Central Markets trading analyst Joe Neighbour.

Without a cash-for-reform deal in the next 48 hours, the chances of Greece averting a default to the International Monetary Fund look slim.

Failure to repay 1.6 billion euros ($1.79 billion) owed to the IMF next week could trigger a bank run and capital controls, and the risk of Greece sliding out of the euro currency area.

Software (Xetra: 330400 - news) company Sage was among the best-performing FTSE 100 stocks, rising 3.1 percent to recover from hefty losses in the previous session as Investec Securities raised its rating on Sage.

Insurance company Admiral fell 1.5 percent after Citigroup downgraded the stock to "sell" from "neutral".

($1 = 0.8931 euros) (Reporting by Alistair Smout; Editing by Keith Weir and John Stonestreet)