With the investigation into the Sept. 11 terrorist attacks slowing in the United States, Atty. Gen. John Ashcroft plans to travel overseas next week to confer with European officials about the next steps in the expanding international war on terrorism, senior law enforcement officials said Friday. FBI officials also confirmed Friday that they are moving to station agents for the first time in China and India, saying improved law enforcement cooperation with those two nations will help in the global fight against terrorism and other crime-fighting efforts. Ashcroft's European trip was prompted in part by the fact that Justice Department officials now believe most, if not all, of the suspects in the Sept. 11 attacks on the World Trade Center and the Pentagon either are in custody in Europe or are being sought by authorities there.