US and Czech government officials said Wednesday they have made headway toward negotiating an agreement to base parts of a missile defense system in the Czech Republic. "I think we've made a substantial amount of progress today," John Rood, US Assistant Secretary of State for International Security and Nonproliferation, said after a new round of talks. But, he added, "We still have work yet to be done." Czech Deputy Foreign Minister Tomas Pojar described the talks, which focused on a bilateral treaty that would cover a radar base the US wants to build near Prague, as "very intensive, and perhaps tough." He said several chapters of the 18-chapter document remain wide open.