Coons announces opposition to Pompeo, cuts off path to favorable committee vote Sen. Chris Coons says he will vote against Mike Pompeo to be secretary of state.

Sen. Chris Coons, a Delaware Democrat, announced Friday that he will not vote to support the nomination of Mike Pompeo to be secretary of state, officially closing the door on Pompeo’s chances of being favorably recommended out of the Senate Foreign Relations Committee ahead of a full Senate floor vote.

Coons, the last Democrat on the panel to announce his position, said in a statement that he was encouraged by Pompeo's commitment to the diplomatic corps that he laid out in his confirmation hearing but concluded that the current CIA director and former congressman would embolden rather than temper President Donald Trump's most bellicose instincts.

“I do not make this decision lightly or without reservations," Coons said in a statement. "I remain concerned that Director Pompeo will not challenge the President in critical moments. On vital decisions facing our country, Director Pompeo seems less concerned with rule of law and partnership with our allies and more inclined to emphasize unilateral action and the use of force."

Coons also said he was concerned with some of Pompeo's past statements made over his political career on "a range of issues."

Republicans on the 21-person committee hold a slim one-seat majority over Democrats. Sen. Rand Paul, R-Ky., also opposes Pompeo's nomination to be the nation’s top diplomat. That meant Pompeo needed the support of at least one Democrat on the committee to get the simple majority needed for a favorable recommendation.

But with Coons’ announcement, all ten Democrats on the committee have now announced that they would not support Pompeo.

Coons’ position is not a surprise. He had said as late as Thursday afternoon that he was “leaning against” Pompeo's nomination and he also voted against him to serve as CIA director last year.

The Senate Foreign Relations Committee will vote on Pompeo’s nomination Monday.

With the option of a favorable recommendation off the table, they can still report the nomination to the Senate floor with an unfavorable recommendation or simply take no action. And the full Senate will still vote on his confirmation, which is likely to succeed.

But the fact that Pompeo’s confirmation will not be referred favorably to the full Senate is an almost unprecedented rebuke from the committee of jurisdiction. The last time any cabinet-level nominee who was reported unfavorably by a committee but went on to be confirmed by the full Senate was 73 years ago when Henry Wallace was confirmed to be the secretary of commerce on March 1, 1945.

Past secretaries of state, including Condoleezza Rice, John Kerry, and Hillary Clinton have breezed through their respective confirmations, receiving strong tallies from both sides of the aisle.

While Pompeo will not receive the support of any of the ten Senate Foreign Committee Democrats, at least one member of the caucus has announced she will vote for him: Sen. Heidi Heitkamp, D-N.D., who is facing a tough re-election fight in a state that voted heavily for President Donald Trump in 2016.

If no other Republican besides Paul opposes Pompeo in the Senate floor vote, Heitkamp’s support means he will have just enough votes to be confirmed, including Vice President Mike Pence’s tie-breaking vote.

ABC's Mariam Khan contributed to this report.