A top ethics official has warned that plans to confirm Donald Trump's top Cabinet choices before background examinations are complete are unprecedented and have overwhelmed government investigators responsible for the reviews.

The concerns prompted Democrats on Saturday to call for delaying the confirmation process, but Republicans signaled they are unlikely to budge on the eve of a slew of hearings in the Senate.

The Trump administration-in-waiting faces its first big test in coming days, with as many as seven nominees for Cabinet positions - many of them already the subject of questions about their qualifications - scheduled to appear on Capitol Hill.

The process begins Tuesday, when Sen. Jeff Sessions, R-Ala., Trump's controversial nominee for attorney general, is scheduled to begin two days of hearings before the Senate Judiciary Committee. But the big show is planned for Wednesday, when five hearings are scheduled, bringing a marathon of nationally televised scrutiny to the thin public records and vast wealth of many of Trump's Cabinet picks.

Democrats have vowed to cast the hearings as a proxy test of Trump himself, in hopes of discrediting his new government before it begins. They hope to remind the public of the president-elect's own lack of government experience and reluctance to separate himself from an entanglement of global business interests while he leads the nation.

But even Democrats acknowledge that Trump's slate of Cabinet picks will probably sail through. The packed schedule, similar to those for nominees of George W. Bush and Barack Obama, was orchestrated by Senate Majority Leader Mitch McConnell, R-Ky., and the Trump team. In addition, Trump has scheduled a news conference Wednesday that will overlap with several hearings, at which he has promised to talk about separating his presidency from his business interests.

Whether the schedule holds in the coming days is unclear. McConnell's office declined to respond to warnings by Walter Shaub Jr., director of the Office of Government Ethics, who said in a letter released Friday the current confirmation calendar is "of great concern to me" because nominees have not completed a required ethics review before their hearings.

The schedule "has created undue pressure on OGE's staff and agency ethics officials to rush through these important reviews," Shaub wrote in response to an inquiry by Democratic senators. "More significantly, it has left some of the nominees with potentially unknown or unresolved ethics issues shortly before their scheduled hearings."

Shaub added: "I am not aware of any occasion in the four decades since OGE was established when the Senate held a confirmation hearing before the nominee had completed the ethics review process."

Republican aides have disputed that notion, saying that in some cases, nominees of both parties have sat for hearings before the paperwork process was completed.

But Democrats struck back Saturday, saying that hearings should be delayed until all paperwork is completed. Sen. Patty Murray, D-Wash., the ranking Democrat on the Health, Education, Labor and Pensions Committee, said consideration of GOP power broker Betsy DeVos to be education secretary should be postponed until OGE finishes reviewing her background and financial investments for possible conflicts of interest or other ethics concerns.

Sen. Richard Blumenthal, D-Conn., condemned what he called a lack of cooperation and communication by the Trump transition and asked for a "timeout" on consideration of nominees until such basic information as an ethics agreement is available to members of the Senate.

"We should put all of these on hold until the background checks by the FBI and the ethics office reports are completed," he said in an interview Saturday.

The OGE enforces federal ethics rules and reviews potential conflicts of interest for nominees to government posts. Shaub, a lawyer and political appointee of President Barack Obama, took over the office in 2013. He donated a total of $500 to Obama's 2012 reelection campaign, federal elections records show.

Ethics experts from both political parties expressed dismay at the possibility that confirmation hearings would proceed before the OGE reviews are completed.

"This is unprecedented," said Trevor Potter, former chairman of the Federal Election Commission who has served as counsel to several Republican presidential candidates and Cabinet nominees in the past. "This suggests that there has been a real breakdown between the transition and the Office of Government Ethics."

Much of the attention this week is expected to focus on Sessions and his controversial record on civil rights, and on ExxonMobil CEO Rex Tillerson, Trump's choice for secretary of state, who has never served in the public sector.

Tillerson is scheduled to appear before the Senate Foreign Relations Committee Wednesday. The health and education panel is set to consider DeVos the same day, while the Senate Intelligence Committee has announced plans to review the nomination of Rep. Mike Pompeo, R-Kan., Trump's nominee for CIA director. Elaine Chao - a former secretary of labor who is married to McConnell - is set to appear before the Commerce Committee to discuss her nomination as transportation secretary.

On Tuesday, in addition to Sessions, retired Marine general John Kelly is scheduled to testify at a Homeland Security committee hearing to review his nomination to lead the Department of Homeland Security.

In a statement, the Trump transition team said Saturday that the president-elect "is putting together the most qualified administration in history and the transition process is currently running smoothly." The statement added that "it is disappointing some have chosen to politicize the process in order to distract from important issues facing our country. This is a disservice to the country and is exactly why voters chose Donald J. Trump as their next president."

McConnell had already vowed Wednesday that "all the president-elect's Cabinet appointments will be confirmed." He called on Democrats to not delay votes on Trump's less controversial choices for national security posts, including Kelly and retired Marine general James Mattis, the nominee for secretary of defense.

"Basically, they can delay the process. They can't stop it," Sen. John Cornyn, R-Tex., said of his Democratic colleagues.

Republicans said they are proceeding quickly in the hope of confirming a handful of Trump picks on Inauguration Day, as happened eight years ago, when seven of Obama's Cabinet nominees were confirmed unanimously on his first day in office.

But Democrats said Obama's nominations moved quickly because nominees had submitted requisite paperwork by early January. On Saturday, Senate Minority Leader Charles Schumer, D-N.Y., said Shaub's warning "makes crystal-clear that the transition team's collusion with Senate Republicans to jam through these Cabinet nominees before they've been thoroughly vetted is unprecedented."

Murray said in an interview last week that Trump "ran his campaign telling people he was about jobs and workers. Many of these nominees don't share that view. Our responsibility is to make sure that we know what we are buying and the country knows what they bought."

Sen. Richard Durbin, D-Ill., said: "We're dealing with more billionaires than we've ever seen in one place in this Trump Cabinet. It creates a special challenge."

Democrats said they plan to focus intently on nominees' business interests and financial disclosures. Several nominees, including DeVos and other picks not yet scheduled for hearings, will probably be grilled over past statements in support of dismantling portions of the departments they have been tapped to lead.

Kelly, Pompeo, Sessions and Tillerson are the furthest along in responding to written questionnaires and divulging personal and financial information, according to Senate aides. But reviews by the FBI and OGE are still underway for most nominees, according to the aides, who are tracking the process but not authorized to speak publicly about details. Sessions's FBI check is complete, but other nominees have yet to complete all of the paperwork required by committees, because the FBI and OGE reviews continue, the aides said.

Many of Trump's picks are widely unknown on Capitol Hill, prompting his transition team to recruit former GOP senators and the party's top-flight communications and policy talent to make introductions and assuage concerns among Republicans and Democrats alike.

Nominees have been scheduled for more than 60 meet-and-greets with senators of both parties, according to Senate aides. Dress rehearsals to prepare for contentious lines of questioning have been underway for several days.

Given Trump's refusal to release tax returns and other financial information during the presidential campaign, Democrats see his Cabinet choices as a way to revive the issue. But if Trump uses his scheduled news conference to divulge details of his finances amid a flurry of confirmation hearings, it may capture the news cycle and neutralize opposition.

While each committee has different disclosure rules for Cabinet picks, just three panels - Budget, Finance, and Homeland Security and Governmental Affairs - have the authority to require nominees to release three years of tax returns. Republicans have rebuffed Democratic requests to force all Cabinet nominees to do so.

Sen. Ron Wyden, D-Ore., the ranking Democrat on the Finance Committee, recalled that his panel's long-standing tax disclosure rules unearthed trouble for several of Obama's Cabinet choices, including former Senate majority leader Thomas A. Daschle, who was forced to withdraw his nomination to serve as secretary of health and human services due to questions about unreported earnings and gifts.

With Democrats vowing to pepper Tillerson about his tenure as an oil executive, Sen. Bob Corker, R-Tenn., who chairs the Foreign Relations Committee, said the former chief executive's decision to completely cut ties with ExxonMobil was "responsible."

"It certainly takes away an issue that we knew had to be taken away," Corker said. "I mean, my very first conversation with him - he knew that, Exxon knew that."

Corker added that Tillerson will probably have "one of the cleaner [financial] disclosures because his whole life and his whole net worth's been in one company."

Some Democrats on the judiciary panel say they have no plans to give Sessions an easy pass, despite his status as a well-liked senator and a former U.S. attorney. Several have vowed to rehash his staunch opposition to immigration reform, his recent support for Trump's call to require "extreme vetting" of Muslim immigrants and his civil rights record. Sessions was denied a federal judgeship in 1986 over charges of racial insensitivity and prejudice.

"A person's whole lifetime career should be considered in such an important position," Blumenthal said in an interview last week. "This position is not just a government lawyer or another Cabinet position. It is the nation's chief enforcer of the rule of law, which is the bedrock of our democracy."

Schumer said last week that Rep. Tom Price, R-Ga., Trump's pick to lead the Department of Health and Human Services and oversee changes to the Affordable Care Act, will endure heavy scrutiny once his hearing is scheduled. Price is bound to face attacks for his support for privatizing Medicare and over stock he has owned in health insurance, pharmaceutical and biotech companies despite serving on a health-care subcommittee.

Schumer and others have called on the House Ethics Committee to begin investigating Price's stock holdings before his confirmation hearing. Republicans noted that several senators on the health panel have similar stock holdings.

Democrats are also targeting Rep. Mick Mulvaney, R-S.C., a fiscal conservative tapped to lead the Office of Management and Budget; Andrew Puzder, a restaurant executive set to serve as labor secretary who opposes raising the minimum wage and has made controversial comments about women; Steven Mnuchin, a billionaire former Goldman Sachs partner set to serve as treasury secretary; and Oklahoma Attorney General Scott Pruitt, who was picked by Trump to lead the Environmental Protection Agency, which he has sued in the past.

Anticipating political combat, Trump's transition office has tapped incoming White House Communications Director Sean Spicer and Bryan Lanza, a veteran of the Trump campaign, to oversee hearing preparations. They are offering strategic advice and sitting in on practice sessions for nominees, according to R.C. Hammond, a transition spokesman.

Party luminaries, including former Texas senator Kay Bailey Hutchison and former Arizona senator Jon Kyl, are also on board to vouch for the nominees, transition officials confirmed.

Kyl was spotted shadowing Sessions at the Capitol last week. Ron Bonjean, a longtime Republican operative who has worked for the Senate and House leadership, also joined the transition team last week as an adviser focused on the most politically sensitive nominees.

Tillerson and Mnuchin, who some Republicans privately worry could face difficult exchanges with senators from both parties, are being assisted by several former officials from George W. Bush's administration.

Mnuchin's team includes Tara Bradshaw, a Bush-era spokeswoman at the Treasury Department, and Mary Waters, an official in the Agriculture Department under Bush. Tillerson's team includes Christian Whiton, who worked at the State Department during the Bush presidency; and Margaret Peterlin, a former Commerce Department official and senior House Republican aide.

Collectively, these former senators and administration officials, who come armed with deep familiarity with the arcane nature of the Senate and the complex policies a nominee will tackle, are known as "sherpas."

But as one transition official quipped: "There's no climbing equipment or walking toward mountains involved."