Tensions over confirming President Donald Trump's cabinet nominees erupted late Tuesday in the US Senate, where a lawmaker's criticism of attorney general pick Jeff Sessions led to the very rare reprimand of a senator.

Senate Democrat Elizabeth Warren was told to sit down for reading a 1986 letter critical of Sessions written by Coretta Scott King, widow of slain civil rights leader Martin Luther King Jr. The chamber's Republican leader Mitch McConnell interrupted Warren to accuse her of having "impugned" Sessions, a fellow senator.

Tensions have soared in the few weeks since Trump took office, particularly over the process of confirming his cabinet nominees.

During debate over education secretary nominee Betsy DeVos, Democrats held the Senate floor Monday through the night as a protest against her nomination.

She was eventually confirmed Tuesday, but only when Vice President Mike Pence was brought in to break a 50-50 tie.

DeVos was sworn in by Pence in a ceremony at the vice president's ceremonial office. Pence said it was "the easiest vote I ever cast." Two Republicans, Susan Collins of Maine and Lisa Murkowski of Alaska, joined Democrats to attempt to derail the nomination of the longtime Republican donor and activist. Pence's vote was the first by a vice president to break a 50-50 tie on a Cabinet nomination.

Pressure built during debate about Sessions, whose record on civil rights ultimately doomed his nomination to a federal judgeship in the 1980s.

At the time King wrote the Senate Judiciary Committee warning that Sessions used to "intimidate and chill" voters, and that confirming him as a judge would have "a devastating effect" on the US justice system. "Mr. Sessions has used the awesome powers of his office in a shabby attempt to intimidate and frighten elderly black voters," she wrote.

Warren, a potential 2020 presidential candidate, was reading the King letter when she was blocked from continuing, a move that astonished Democratic Senator Sheldon Whitehouse.

An exasperated Senator Orrin Hatch, the longest-serving Republican currently in the Senate, called for a more dignified debate of Trump's nominees.

Senators must treat one another with respect, "or this place is going to devolve into nothing but a jungle," he said.