The Senate Intelligence Committee is in talks to interview Christopher Steele, the former British intelligence operative who compiled the dossier that alleges a conspiracy between the Trump campaign and Russia, three sources with direct knowledge told NBC News.

Steele, however, remains concerned about his safety and is not inclined to leave London. He is also concerned about how he might be treated by the Trump administration, according to the sources. The FBI was poised last fall to pay Steele, a former officer with the British Secret Intelligence Service, for information, but that deal fell through, sources familiar with the matter told NBC News.

Two Congressional officials told NBC News that the Senate Intelligence Committee has not yet reached an agreement on how and when to interview the Trump associates who have volunteered to testify, including Paul Manafort, Carter Page and Roger Stone. If any of those men seek criminal immunity for their testimony, the committee would not be inclined to grant it, officials say. The committee could then subpoena them, but they could assert their Fifth Amendment rights and refuse to answer questions.