Democrats on the US Senate Finance Committee are boycotting votes for two of President Donald Trump's cabinet nominees, forcing a postponement.
They said they wanted more information about the financial activities of health nominee Tom Price and treasury pick Stephen Mnuchin.
Other Trump choices face votes, among them Jeff Sessions as attorney general.
On Monday the acting attorney general was sacked for questioning the legality of Mr Trump's immigration directive.
It imposes a temporary travel ban on seven mainly-Muslim countries.
Acting Attorney General Sally Yates had been appointed by President Barack Obama.
Finance Committee Democrats told reporters outside the hearing that they were seeking more information about Tom Price's trading in health company stock.
The Georgia Congressman has been nominated for the post of health and human services secretary in the new administration.
The senators said they were also concerned by reports of financier Stephen Mnuchin's behaviour involving foreclosures at his former bank OneWest.
But Senator Orrin Hatch, the Republican committee chair, described the Democrats' behaviour as "posturing and acting like idiots", AP reported.
Democrats get tough, by Anthony Zurcher, BBC News
The unexpected walkout by Democrats during scheduled votes to advance two of Donald Trump's more controversial cabinet nominees may be the first shots that lead to total partisan warfare on Capitol Hill.
Democratic senators had been subjected to growing criticism from the grass-roots Left for being too accommodating to Mr Trump and his nominees. On Sunday, for instance, more than 200 protesters descended on Senator Diane Feinstein's California house after she voted to confirm four earlier administration nominees.
Now, it seems, Democrats could be heeding the anger of their base and taking a more combative posture toward Republicans in general and Mr Trump in particular. These politicians likely saw Acting Attorney General Sally Yates become a liberal hero for defying the president on Monday night and are recognising that their party's anger is a force that could propel their careers or tear them apart.
This does not bode well for Mr Trump's Supreme Court nominee, who will be announced on Tuesday night. While Senate Democrats have had to rely on byzantine parliamentary manoeuvres to delay Mr Trump's cabinet picks, they have a powerful weapon - the filibuster - at their disposal to indefinitely block the president's high court selection.
A battle is also raging in the Senate Judiciary Committee, where a vote is expected on Mr Sessions.
An early Trump backer, Senator Sessions has faced racism allegations which overshadowed his confirmation hearings.
Committee chairman Senator Chuck Grassley began Tuesday's meeting by saying that neither Mr Sessions nor any of his current staff, "had a role in formulating or drafting the executive orders" - including the controversial travel ban.