Intercontinental Exchange Inc.'s New York Stock Exchange has agreed to acquire National Stock Exchange Inc.

National Stock Exchange will continue to operate as a licensed national market system exchange, subject to the SEC's approval. It no longer has plans to cease trading on Dec. 16 as it previously announced.

The acquisition will increase the NYSE Group's U.S. exchange licenses to four. National Stock Exchange will be distinct from NYSE's three listing exchanges, NYSE, NYSE MKT and NYSE Arca Equities.

The transaction is expected to close in the first quarter of 2017, subject to regulatory approvals. The terms of the transaction were not disclosed.