* FTSEurofirst 300 flat, Euro STOXX 50 down 0.1 pct
* Wait-and-see mode ahead of ECB meeting
* New ECB measures seen as priced in already
* Holcim, Lafarge rally on private-equity bid report (Updates prices)
By Lionel Laurent and Blaise Robinson
LONDON/PARIS, June 4 (Reuters) - European shares held steady on Wednesday after data confirmed a slowdown in the euro zone's economic recovery in the first quarter, with investors awaiting fresh action by the European Central Bank to spur growth.
The 18-nation bloc's economy expanded by just 0.2 percent in the three months to March, statistics office Eurostat said, cementing investor expectations for the ECB to trim its refinancing rate, send its deposit rate into negative territory and launch a cheap-lending initiative targeted at businesses.
The FTSEurofirst 300 index of top European shares closed flat at 1,374.75 points, hovering below a 6-1/2-year high hit on Monday.
"No-one's really eager to make any aggressive moves ahead of tomorrow," said CMC Markets analyst Jasper Lawler.
"It seems unlikely the ECB would disappoint in terms of action...(But) the real crunch is going to be what the ECB guides for the next meeting and beyond."
The market's pause for breath left national benchmark indexes in France, Britain, Italy and Spain down between 0.1 and 0.3 percent, while Germany's DAX index ticked up 0.1 percent.
Stocks in the euro zone's more vulnerable economies have been rallying on hopes of radical policy measures from the ECB to fend off the risk of deflation. Milan's FTSE MIB index is up 14 percent for the year-to-date and Madrid's IBEX up 9 percent.
Shares of Spanish oil-and-gas company Repsol fell 3.6 percent, one of the worst performers on the FTSEurofirst 300, after Mexico's Pemex sold the bulk of its stake in Repsol for 2.09 billion euros ($2.85 billion).
Construction companies Holcim and Lafarge rallied more than 2.8 percent after a report said that private-equity companies were considering bids for some assets as part of the companies' planned merger.
Hopes for ECB intervention have often prompted a bullish investor response to weak data in recent months. Now some traders see a growing risk of a pullback after the central bank's meeting on Thursday.
"There's a real danger the ECB has created a rod for its own back (with expectations)," said Nick Beecroft, analyst at Saxo Bank.
"The risk is that if some of the expected measures are announced but not all of them, the market strengthens the euro and tries to force the ECB into more action."
Shares in Tesco fell 1.3 percent after Britain's biggest retailer posted its worst quarterly UK sales drop in 40 years on Wednesday, ratcheting up the pressure on boss Phil Clarke to show his turnaround plan can address the challenges of the grocery industry.
Europe bourses in 2014: link.reuters.com/pap87v
Asset performance in 2014: link.reuters.com/gap87v
Today's European research round-up ($1 = 0.7342 Euros) (Editing by Pravin Char and Ruth Pitchford)