Semantics

At the press conference, webcast in both English and German, Francioni argued that the deal "reshapes our entire industry," and would strengthen the roles of both New York, as the financial capital of the world, and Frankfurt, as a European financial capital.

Though the tie-up is seen in part as a defensive move, Niederauer said it was "no act of desperation," adding that he assumed it will be subject to a US government foreign investment review.

Indeed, he said that the deal will put the merged company in a strong position to do deals elsewhere -- making it "the inviter, the enabler, the convener with other exchanges in Asia and the developing world down the road."

In one exchange with a reporter, the CEO said news media could help lawmakers understand the deal by calling it a merger. "I don't know how many more times I have to say that," Niederauer said. "And I guess each time I say that -- you know I love you guys, but you keep saying it's an acquisition."

US Senator Charles Schumer, who first raised the name issue over the weekend, has been insisting that NYSE should come first in the title of the group, which will have headquarters in both New York and Frankfurt.

Schumer reiterated those concerns after the deal was announced on Tuesday, calling the NYSE a "preeminent brand" and saying there was no reason for it not to come first. France has also expressed concerns over benefits that will fall to Paris.

There also remains a chance that some other US exchange could get involved in a counterbid for NYSE. Officials from exchange companies CME Group Inc and Nasdaq OMX Group will meet to discuss a "strategy to respond" to the buyout deal, Fox Business Network reported on Tuesday.

Niederauer said he was aware of the rumor of a possible CME bid for NYSE but had heard nothing official, adding that the Big Board had signed a deal with a partner that it trusts.

The exchanges face intense competition in their traditional stock-trading business from newer trading venues geared toward today's increasingly dominant high-speed electronic traders.

NYSE -- created in 1792 by brokers and merchants who met under a buttonwood tree in lower Manhattan -- is one of several exchanges that have responded by investing in technology and pushing hard into futures trading.

But the Big Board's once dominant market share in US equities trading has steadily dwindled in recent years, and NYSE Euronext shares are down 61 percent since early 2007.

Together, the companies dominate futures and options on European bonds, shares and rates, with Deutsche Boerse's Eurex unit focused on the long end of the interest rate curve and NYSE Euronext's Liffe unit on the short end.

"This merger -- if approved -- creates a true thousand-pound gorilla," said Herbie Skeet, analyst at exchange consultancy Mondo Visione.

Shortly after the 90-minute press conference, the Frankfurt-based company reported a 16 percent fourth-quarter profit drop.

NYSE shares closed trading on Tuesday down 3.4 percent at $38.12, while Deutsche Boerse shares slid 2.4 percent. Given the time the deal will take to complete, NYSE's shares are expected to trade below the offer price, unless another bidder emerges.