(CNN) After President Donald Trump signaled he will cut humanitarian aid to the Northern Triangle -- Guatemala, El Salvador and Honduras -- and threatened to close the southern border with Mexico, key diplomatic posts in those countries remain empty.

There is no ambassador in Honduras and no nominee for the job. The administration only last week sent its nomination for ambassador to Mexico, Christopher Landau, to the Senate and a congressional Democratic aide suggested that his lack of diplomatic experience is bound to come up in his confirmation hearing.

In addition to Mexico and Honduras, a number of other key posts remain unfilled. Ambassador posts in Egypt, Jordan and Brazil, for example, do not have ambassadors or nominees, according to the American Foreign Service Association. There is no US ambassador to the United Nations. There are more than a dozen empty ambassador posts without nominees, according to AFSA.

Also, of the nine top positions at the Department, including the secretary and his deputy, only four are filled with permanent picks. The rest are either vacant or temporarily held by "acting" choices.

Overseas posts face gaps as well. Last month the US Government Accountability Office studied the persistent State Department vacancy rate, predating the Trump administration — of about 13%, including places key to US interests — finding that State lacks "an integrated action plan" to fix the problem. The report states, "As a result, State's ability to achieve US foreign policy goals and help ensure secure and efficient operations could be adversely impacted."

And the back and forth over who is to blame for the vacancies continues to play out.

Blame game

The Trump administration has long blamed the Senate -- and in particular, Democrats, despite the fact they aren't in control -- for holding up nominees to eventually fill the vast number of vacancies within the State Department.

But congressional sources and the Senate Foreign Relations Committee's top Democrat Bob Menendez are pushing back, accusing the White House of repeatedly sending nominees who they believe are unqualified.

"While Mr. Landau deserves every right to have his nomination carefully considered, the fact is he has no relevant experience for this critical post except for having his dad's CV attached to his name. I find it hard to imagine his lack of experience not coming up during his confirmation process," the Democratic aide said of the nominee for ambassador to Mexico, referring to the fact that Landau's father was a diplomat. Landau did not immediately reply to a request for comment.

In a speech on the Senate floor last week, Menendez angrily hit back at accusations that the Senate was intentionally holding up nominees, pointing to the many issues other nominees face.

"The President has nominated and re-nominated individuals with restraining orders for threats of violence; people who made material omissions, sometimes on a repeated basis, in their nomination materials; people who tweeted and retweeted vile things about Senators and their families; and who have engaged in incidents that should, frankly, mean they never should have been nominated," Menendez said. "So when the White House, either through negligence or incompetence, sends us un-vetted, unqualified nominees, incapable and often times offensive, my staff and I must exercise due diligence on behalf of the American people."

Senate Republicans acknowledge that the Trump administration does have a tendency to get ahead of itself in announcing nominees before they are fully vetted, often doing so mid-way through the process, but insist the same standard of vetting is being applied as under previous administrations, according to a senior Senate aide.

'This is not rocket science'

Menendez also said the administration had many times simply failed to put forward nominees, or had done so late, then launched into an extended list of instances in which he said the President had nominated unqualified and seemingly unvetted candidates.

"One nominee attacked my late colleague and good friend, Sen. John McCain, claiming that John McCain, an American hero, was rolling 'out the welcome mat for ISIS on America's Southern Border,'" Menendez said, referring to Ronald Mortensen. Mortensen, who was nominated to be an assistant secretary for the Bureau of Population, Refugees and Management, made that claim in a 2014 opinion piece. His nomination was returned to the President in January. Mortenson did not immediately reply to a request for comment.

"Another nominee has claimed, with no evidence, that the wife of Sen. Cruz is part of a sinister cabal seeking to combine the governments of Canada, Mexico and the United States. This nominee called Hillary Clinton a 'terrorist with amnesia,' and retweeted someone calling Sen. Romney a 'dumba**','" Menendez continued in a reference to Leandro Rizzuto Jr., Trump's nominee for ambassador to Barbados and several other Caribbean countries. CNN's KFile reported in February 2018 that Rizzuto, who was nominated in 2018 and re-nominated in 2019, spread fringe conspiracy theories online. Reached by phone at the time, Rizzuto told CNN that he could not comment based on guidelines from the State Department.

A congressional source tells CNN that in the last Congress, the Senate Foreign Relations Committee confirmed 144 of 169 nominees. Menendez had cleared 24 of the 25 remaining nominees, but they were held up for other reasons, including some by Republican senators.

The source added that in the current Congress, Menendez has just cleared 20 more of the White House's nominees.

The source said that, on average, State Department nominees have been confirmed at nearly the same rate as during the Obama administration: an average of 74 days, compared to 63 under Obama. The source blamed that gap, largely, on the "poor vetting" and "ridiculousness" of nominees proposed by the current administration.

Menendez summed up, "So, to make this crystal clear, the President can speed up this process. All he has to do is start nominating Americans with appropriate credentials and honorable conduct in their careers. This is not rocket science."

Former Fox News presenter Heather Nauert's pending nomination for UN Ambassador had been announced, then abruptly withdrawn , when it was discovered that she had, for years, employed a foreign nanny not authorized to work in the United States, and hadn't paid the required taxes. But this was discovered long after Nauert had already been confirmed and working at the State Department as its spokesperson.

While Nauert no longer conducts public briefings, she is still employed by the Department, though the White House is expected to replace her with another Fox News alumna. Nauert did not immediately return CNN's request for comment on the tax issue. Upon withdrawing from consideration, she said, "I am grateful to President Trump and Secretary Pompeo for the trust they placed in me for considering me for the position of US Ambassador to the United Nations. However, the past two months have been grueling for my family and therefore it is in the best interest of my family that I withdraw my name from consideration."

Examples that particularly rankle some Hill staffers include Christine Toretti, nominated to be ambassador to Malta, who had a restraining order issued against her in 2008 for allegedly threatening her ex-husband's doctor by placing a bullet-riddled target practice sheet on his office chair. The restraining order, according to reporting in the Arizona Daily Sun at the time, said the piece of paper was shot through with 25 bullet holes. She did not immediately return a request for comment for this story.

Kyle McCarter, an Illinois businessman and former State Senator, now Ambassador to Kenya, faced a battle in the Foreign Relations Committee over his opposition to gay marriage and his 2016 Election Day tweet that Hillary Clinton should be sent to prison. Republican Sen. Johnny Isakson, who was chairing McCarter's confirmation hearing, told him to address the meaning of the tweet — in writing. McCarter did so, and Isakson's office told CNN he was satisfied with the response.

Billionaire hotel developer Doug Manchester, who goes by the nickname "Papa Doug" and is the Trump administration's nominee for ambassador to the Bahamas, apologized to the multiple women who publicly said they felt "uncomfortable or demeaned" during the time Manchester owned The San Diego Union-Tribune.

According to the Washington Post, "During the taping of a promotional video, Manchester once pulled a reporter in for a hug so intimate that it startled onlookers in the newsroom, multiple people said. He complimented young female employees on their looks, and he and other senior managers required some of them hired for a new in-house television operation to wear short black dresses and serve as hostesses for advertisers and other guests at Union-Tribune events, current and former employees said."

In a statement to The Post at the time, Manchester said, "I have never been accused of or sued for any kind of sexual misconduct."

"I am terribly hurt to learn of these allegations and apologize to any employee who felt uncomfortable or demeaned while employed at the UT San Diego during my tenure," he said.

But Manchester also made waves when, under questioning by US Senators, he referred to the Bahamas as a "protectorate" of the United States. The island group is an independent nation. A number of senators, according to a congressional source, believed that he ought to have known that

'Highly qualified people that have been held up'

Meanwhile, on the other side of Capitol Hill, Secretary of State Mike Pompeo directed blame at the Senate.

"We especially need extremely qualified individuals we nominated to serve in important management positions across the department, many of whom have been awaiting Senate confirmation since last year," Pompeo said in his opening remarks at a House Foreign Affairs Committee hearing last week.

Asked about "staffing shortfalls," Pompeo said there were "highly qualified people that have been held up."

"They're sitting in the United States Senate today," he said.

Last week's clash of words were the latest in an ongoing feud between Menendez and Pompeo on nominees. In an October statement on Nikki Haley's announcement she would step down as UN ambassador, Menendez wrote "This administration's continued inability to adequately or appropriately fill key national security positions puts our nation at risk."

Pompeo fired back, accusing Menendez and Senate Democrats of "putting our nation at risk" by not voting on nominees.

"These outstanding candidates remain unconfirmed because Sen. Menendez and some of his colleagues are using our nominees as a political football," Pompeo said in a statement.

One Republican source on Capitol Hill commented on the tough back-and-forth in a single line: "The confirmation process speaks for itself."