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By Jonathan Spicer

NEW YORK, June 24 (Reuters) - The New York Stock Exchange is likely to extend a reprieve for companies facing delisting from the Big Board beyond June 30, despite this quarter's strong rebound in U.S. stock prices, the head of NYSE Euronext (NYX.PA: Quote, Profile, Research)(NYX.N: Quote, Profile, Research) said on Wednesday.

In February, the Big Board suspended its requirement that companies keep their shares above $1 or face delisting, a decision it said at the time would help keep more than 50 companies' shares on the exchange.

It also decided at the time to extend a temporary rule allowing companies to maintain listings if their market value were $15 million, rather than $25 million. NYSE's moves, meant to stem a flood of delistings, were similar to ones at rival Nasdaq Stock Market.

"I would imagine we'll extend it a little longer, but it definitely will not be a permanent change," NYSE Euronext CEO Duncan Niederauer told the Foreign Press Center here.

"I want to be comfortable that most of the companies that we're worried about are now in the safe zone" before reverting to the original listing requirements, he said.

A spokeswoman said Nasdaq OMX (NDAQ.O: Quote, Profile, Research) had no comment on whether its reprieve would extend beyond its July 19 deadline. Nasdaq first suspended its minimum-price listing requirement in October.

The U.S. Securities and Exchange Commission needs to approve such rule changes at the two exchange operators, which each derive between 10 and 15 percent of overall revenue from listings.