Clara Furse , chief executive of the London Stock Exchange , wants to keep its unwelcome suitor, Nasdaq , at bay — and now she has put money on it.

On Thursday, Furse and the London exchange pledged to buy back as much as ?250m ($493m) in shares this year, an offer that would increase the exchange's debt enough that Moody's has put the stock on watch for a possible downgrading.

The London exchange also reiterated that Nasdaq's offer of ?12.43 a share was “wholly inadequate.” Furse said she was in talks with other exchanges, but would not specify which ones. The discussions, she said, were about “cooperation” and the “opportunity to consolidate.”