WASHINGTON (AP) — President Joe Biden unveiled two more ambassador nominees Wednesday, but the White House and Democrats warned that maneuvering by some Senate Republicans to block all but a small fraction of diplomatic and other national security appointees is doing serious harm to U.S. efforts around the globe.

Senate Majority Leader Chuck Schumer has threatened to keep lawmakers who are eager to get home for Christmas at work in Washington into next week if progress isn't made on the backlog of more than 70 ambassadorial nominees awaiting votes.

Biden administration officials acknowledge the president will almost certainly end his year with significantly more ambassadorial vacancies than any of his recent predecessors and that the slowdown of ambassadorial and other national security picks has already had an impact on U.S. relations overseas.

"It's long past time for GOP senators to get out of the way and let the Senate quickly confirm these national security nominees so they can advocate for the interests of the American people around the world," said White House principal deputy press secretary Karine Jean-Pierre.

As of Tuesday, only 13 of Biden's 85 ambassadorial nominees have been confirmed by the Senate, according to the White House.

At the same point in the three previous administrations, presidents had far more of their diplomats confirmed and installed at embassies around the globe. Donald Trump had 44 of his 60 nominees confirmed, Barack Obama 72 of 96, and George W. Bush 93 out of 103.

Much of the White House and Schumer's frustration has been pointed toward a few Senate Republicans who have set roadblocks — most notably Republican Sen. Ted Cruz of Texas — by using holds and other procedural maneuvering to slow dozens of ambassador and other appointments at the departments of Defense, Homeland Security and State.

Republican pressure is also mounting on Cruz over the holds.

"We just need to get some people in place," said Sen. Lindsey Graham, R-S.C., pointing to diplomatic vacancies such as those for China and Japan. He added: "It's a dangerous world out there right now."

Cruz on Wednesday said he had offered to lift holds on 16 nominees in exchange for a Senate vote on sanctioning the companies behind Nord Stream 2 — a controversial Russia-to-Germany natural gas pipeline.

Critics on the both sides of the aisle have raised concerns that the pipeline will threaten European energy security by increasing the continent's reliance on Russian gas and allowing Russia to exert political pressure on vulnerable Eastern and Central European nations, particularly Ukraine.

Schumer countered that the Texas Republican must lift his holds on all nominees from the State and Treasury departments and the U.S. Agency for International Development.

"Let's be clear about the nominees at issue. We aren't talking about partisan firebrands or candidates that come out of left field. The bulk of these men and women are uncontroversial, by-the-book, professional public servants," Schumer said.

Cruz was defiant, suggesting "Schumer has decided that he wants no ambassadors confirmed. That's a really foolish decision for him."

The Senate typically confirms noncontroversial State Department and Pentagon nominees by unanimous consent, a process that doesn't require the Senate to use valuable floor time. Many of the nominees being held up were voted out of the Foreign Relations and Armed Services committees with broad bipartisan support.

A hold by a senator doesn't block a nominee from being confirmed. It just requires more time-consuming steps to get to a final vote. So far, Democrats have chosen to prioritize the confirmation of federal judges.

Overall, Biden has nominated 174 people for national security positions in the departments of Defense, Homeland Security and State that require Senate confirmation. Sixty-three, or about 36%, have been confirmed.

Sen. John Thune, the Senate's No. 2 Republican, said many in the GOP caucus are hoping Cruz "can find a way forward to work with Democrats to get to some of these positions filled."

"I think there are members who are really concerned about particularly certain areas of the world where we don't have ambassadors in place and recognize that it's important that some of these get done," Thune said.

Even with the backlog, Biden continues to send new nominees to the Senate for confirmation.

The president on Wednesday announced he will nominate Caroline Kennedy, a former U.S. envoy to Japan in the Obama administration and daughter of the late U.S. President John F. Kennedy, to serve as his chief envoy to Australia and retired U.S. Olympic figure skater Michelle Kwan to serve as ambassador to Belize.

Publicly, White House officials have lauded career foreign service officers who have stepped up at embassies to try to fill the void as the administration awaits confirmation of ambassadorial picks.

But the blockade has already had real impact on U.S. foreign policy and national security interests in hot spots around the globe, officials say.

In China — perhaps the most complicated and consequential foreign policy relationship — Biden's foreign policy advisers worry that the lack of a Senate-confirmed diplomat has sent the message to Beijing that the U.S. Embassy there lacks an envoy who truly speaks for the president, according to an administration official who was not authorized to comment publicly and spoke on the condition of anonymity.

Republican Sen. Marco Rubio of Florida announced in November that he had put a hold on the nomination of Nicholas Burns to be ambassador to China in an effort to press Biden to sign into law bipartisan legislation he co-authored banning products made with Uyghur forced labor in western China.

The White House said Tuesday after the House passed the bill that Biden would work closely with Congress to implement it. Rubio said he was open to lifting the hold on Burns "if we can get it passed and signed by the White House."

"I still have concerns about whether he's the right person, but in the end, he's going to get a vote. It's an important post," Rubio said of the nominee.

Biden's ambassador to NATO, Julianne Smith, came to the post last month, shortly after Republican Sen. Josh Hawley of Missouri removed a hold on her nomination. Her confirmation vote came after Russia had already begun massing thousands of troops on its border with Ukraine.

Russia has signaled that its military maneuvering — which has put Washington and much of Europe on high alert about a potential further Russian invasion of Ukraine -- was tied to its concerns about NATO expanding to Ukraine.

Hawley has put holds on other State Department nominees to show his disapproval of the administration's handling of the chaotic U.S. withdrawal from Afghanistan.

Former Sen. Jeff Flake, a Republican, waited more than three months for his confirmation vote in late October to become ambassador to Turkey.

The White House could have used Flake's help in August as it sought to win Turkey's help in securing the Kabul International Airport ahead of the withdrawal from Afghanistan, the official noted.