Comments from Republican lawmakers on Sunday presaged a fierce confirmation battle for the man U.S. President Barack Obama is reportedly about to nominate as his defense secretary: Chuck Hagel.

Obama has decided he wants the 66-year-old former Republican senator to succeed Leon Panetta at the Pentagon and will make his announcement as early as Monday, U.S. media, including CNN and Washington specialists Politico, said.

The administration of President Barack Obama is considering a broad array of measures to curb the nation's gun violence, including more than just a reinstatement of a ban on assault weapons and high-capacity ammunition, The Washington Post reported Sunday.

Citing multiple people involved in the administration's discussions, the newspaper said a working group led by Vice President Biden is seriously considering several measures: universal background checks for firearm buyers, tracking the movement and sale of weapons through a national database, strengthening mental health checks, and stiffening penalties for carrying guns near schools or giving them to minors.

The Taliban on Saturday warned of a prolonged war in Afghanistan if any foreign troops stay after the end of 2014, as Kabul and Washington prepare to discuss the "residual" U.S. security presence.

President Barack Obama and President Hamid Karzai will hold talks in the U.S. next week on a long-term security pact between the two countries, with U.S. troops remaining in Afghanistan at the top of the agenda.

Stanley McChrystal, the former U.S. commander in Afghanistan who was sacked by President Barack Obama over a magazine interview, said Friday his new memoir steers clear of gossip and scandal.

The retired four-star general's book, "My Share of the Task," is due out next week but he said he avoided settling scores in his account of his military career, which included clashes with Obama's advisers over the Afghan war.

Congress certified Friday what the world has known for nearly two months -- President Barack Obama's re-election, which was made official through the counting of the Electoral College's votes.

Only then, after votes from each of the 50 states and the District of Columbia were tabulated, was Obama officially declared the winner over Republican Mitt Romney -- a quaint formality, perhaps, but also constitutionally required.

President Barack Obama has signed into law a contentious compromise bill hammered out in Congress that narrowly averted the U.S. 'fiscal cliff of tax hikes and drastic, immediate cuts in spending, the White House said early Thursday.

In a statement, the White House said that Obama late on Wednesday signed the "American Taxpayer Relief Act of 2012," raising taxes on households earning above $450,000 and delaying spending decisions for two months.

President Barack Obama said Tuesday he had fulfilled a campaign promise to make the U.S. tax system fairer with a deal to avert the fiscal cliff crisis that passed after a fierce duel in Congress.

"The one thing that I think hopefully in the New Year we'll focus on is seeing if we can put a package like this together with a little bit less drama, a little bit less brinksmanship, not scare the heck out of folks quite as much," he said.

Iran on Tuesday blasted U.S. President Barack Obama for enacting a law aimed at countering Tehran's alleged influence in Latin America, saying it was an overt intervention in the region.

"It is an overt intervention in Latin American affairs... that shows they are not familiar with new world relations," Iranian foreign ministry spokesman Ramin Mehmanparast told reporters.

U.S. President Barack Obama said in an interview broadcast Sunday that the massacre at a Connecticut elementary school which killed 20 young children was "the worst day of my presidency."

Obama also expressed skepticism about a proposal by the gun lobby group The National Rifle Association to introduce armed guards in every U.S. school and admitted there would be resistance to new proposals to control firearms.

President Barack Obama enacted a law Friday to counter Iran's alleged influence in Latin America, through a new diplomatic and political strategy to be designed by the State Department.

The Countering Iran in the Western Hemisphere Act, passed by lawmakers earlier this year, calls for the State Department to develop a strategy within 180 days to "address Iran's growing hostile presence and activity" in the region.