The Romulan Conference.
The Romulan Conference was a conference between the United Federation of Planets and the Romulan Star Empire that was held on Romulus in 2375. Admiral William Ross was the senior Starfleet member at the conference. The Federation attendees were brought to the conference aboard the USS Bellerophon.
Julian Bashir, the Federation's leading expert on Dominion biogenic weapons and ketracel-white was invited to the conference. He was to talk about the biogenic weapons and to chair a seminar on the drug.
The rogue intelligence group Section 31 saw the conference as an opportunity to elevate Koval, a Federation informant, to the powerful Continuing Committee. (DS9: "Inter Arma Enim Silent Leges")