U.S. Attorney General Eric Holder on Friday urged Congress to move quickly to pass a package of gun control measures proposed by the White House earlier this week.

Speaking at the U.S. Conference of Mayors in the capital, Holder called for immediate congressional action, to make " significant strides in reducing the violence that too often fills our headlines and afflicts our communities."

"Some have said that these changes will require tough votes, by members of Congress. As you all know, public service is never easy, and there come times when those of us who are elected or appointed to positions must put the interests of those who we serve -- who we are privileged to serve, above that which might be politically expedient or professionally safe. This is one of those times," said Holder, who will stay on as the head of Justice Department in Obama's second term.

The Attorney General urged lawmakers to enact the "common-sense legislations" which President Barack Obama announced on Wednesday, including universal background checks of gun sales and bans on military-style weapons and high-capacity magazines.

The gun reform could begin with completing the background checks system, a "relatively simple step", said Holder.

"Congress should move swiftly to adopt legislation to require universal background checks so that a full background check is conducted every time someone attempts to buy a gun," said Holder.

He encouraged more private sellers to work with licensed dealers to ensure that all sales are subject to a comprehensive background check.

Obama on Wednesday unveiled a sweeping package of gun violence reduction proposals, a month after the Sandy Hook Elementary School mass shooting that killed 26 people including 20 schoolchildren. The measures include 23 executive actions which the president signed at the scene, and proposals that require the Congress to adopt relevant legislation to renew a ban on military- style assault weapons, impose a 10-round limit on ammunition magazines and expand background checks for all gun sales.

The measures, quickly assembled by a White House task force headed by Vice President Joe Biden after the December massacre sparked a nationwide debate on gun-control necessity, was deemed as the most sweeping gun-control effort in the United States in nearly two decades.

However, much of the extensive federal agenda is expected to meet resistance on Capitol Hill, where hearings will be held in the next two weeks to consider those proposals, first in the Democratic-controlled Senate and then the GOP-controlled House.