There are new signs that relations are very tense between President Trump and the special counsel in the Russia investigation. According to the Washington Post, Robert Mueller has told the president's lawyers that Mr. Trump might be subpoenaed if he doesn't agree to answer investigators' questions.

After 19 indictments it doesn't look like the Russia investigation will end without Mueller questioning the president -- at least that's what the special counsel is signaling. The ongoing negotiations with the president's legal team have become contentious and it is unclear what will come next.

In January, President Trump told reporters he was interested in talking with Mueller under oath, but behind the scenes, the president's lawyers have been carefully negotiating the terms of those possible talks, reports CBS News' Jeff Pegues.

In one meeting with Mueller, according to the Washington Post, the lawyers insisted the president had no obligation to talk. Mueller responded that he could "issue a subpoena for the president to appear before a grand jury." The episode highlights the escalating showdown between the White House and the special counsel.

"The bare minimum for Mueller is going to be to get some answers from Trump under oath. No prosecutor would settle for less. And any answers under oath by Trump puts him in serious criminal jeopardy," former Department of Justice official Harry Litman said.

Republicans are also taking aim at Deputy Attorney General Rod Rosenstein – who oversees Mueller's investigation.



"I can tell you that there have been people who have been making threats privately and publicly against me for quite some time," Rosenstein said Tuesday.

On Tuesday, Rosenstein pushed back against reports that Republican lawmakers were drafting articles of impeachment against him. Republican members of the House Freedom Caucus say impeachment would be used against Rosenstein as a "last resort" if he doesn't comply with requests for information pertaining to the Russia investigation.

"I think they should understand by now the Department of Justice is not going to be extorted," Rosenstein said.

A subpoena has always been an option for the special counsel to use, but to use it to compel a president to testify could lead to a legal battle in the Supreme Court. Neither the special counsel nor the Trump legal team is commenting.