House Democrats on Thursday urged President Obama to take "bold" executive action to stop the deportation of millions of undocumented immigrants, and vigorously defended his authority to do so despite GOP claims of presidential overreach.

The Democrats argued that because the GOP-controlled House has not passed an immigration reform bill, even after the Senate passed a sweeping measure last year, Obama is more than justified to move ahead on his own.

"I urge the president, in light of all that is has happened, to take action, and my prediction is that if he does, then we will take action," said House Minority Whip Steny Hoyer (D-Md.).

Hoyer spoke at news  conference with about two dozen Democratic colleagues that was led by Rep. Luis Gutierrez (D-Ill.), a vocal immigration advocate. Gutierrez encouraged Obama not to be timid.

"What we want the president to do is act big act, act bold, act broadly and act soon," he said. Gutierrez encouraged the president not to wait until after an upcoming government spending bill is settled. Some Republicans have suggested such a bill could be a vehicle for fighting the president on immigration.

The Illinois Democrat said he has not been briefed on the details of the White House's ultimate plan and he would not confirm a New York Times report that the president is prepared to protect up to 5 million undocumented immigrants against the threat of deportation, and offer work permits to many undocumented parents of legal citizens and residents.

“We don’t know what the number [is] the president is considering,” he said.

Rep. Zoe Lofgren (D-Calif.), who said House Democrats are in “constant communication” with the White House, added, “I don’t know who leaked that to the New York Times, but I don’t believe it reflects necessarily what is happening at this moment.”

Gutierrez referred to himself as the “muscle” behind the push for immigration reform, and Lofgren as the “brains” of the operation.

House Republicans have threatened a response of some kind to Obama if he uses the power of executive fiat to remake the nation’s immigration policies. But the Democrats argued that it is precisely because of the House GOP that Obama has to go it alone.

"It is critical that President Obama do what they will not," said Rep. Ben Ray Lujan (D-N.M.).

Republicans have warned that Obama would be going too far by using his powers to make sweeping changes. But Democrats said the president is well within his bounds, drawing from history to bolster their claims.

“Abraham Lincoln signed the Emancipation Proclamation and there was much to be said about it at the time. But he led with executive action,” said Rep. Al Green (D-Tex.). Green later added: “When Truman signed the order desegregating the military, there was much being said. But it desegregated the military.”

Added Lofgren: “Presidents have broad authority and have used it for decades.”