CSX and Berkshire Hathaway-owned BNSF on Friday announced new coast-to-coast services, a move that strengthens their freight connectivity but that tempers market expectations of an imminent merger between the two rail giants.

CSX ( NASDAQ: CSX) remains open to an approach from Warren Buffett's ( NYSE: BRK.B) BNSF, but no offer has been made, according to CNBC's David Faber on Monday. There "have not been any talks of any kind involving an actual acquisition," Faber said on the business network. "They haven't been approached. They haven't gotten an offer at CSX."

CSX may also be responding to activist pressure, the TD Cowen analysts said. Ancora Holdings has been pushing CSX to either pursue a deal with a rival or replace its chief executive, The Wall Street Journal reported this month.