President Obama will unveil sweeping gun control proposals this week that could include a ban on semi-automatic assault weapons, a limit on magazine rounds, more extensive background checks for gun buyers and other reforms the president is threatening to enact without congressional approval.

"My starting point is to focus on what makes sense, what works, what should we be doing to make sure that our children are safe and that we're reducing the incidents of gun violence," Obama said at a White House press conference Monday.

Vice President Biden has been crafting a legislative plan to reduce gun violence following the murder of 20 elementary school children in Connecticut in December, and Obama is expected to announce this week what measures he'll send to Congress.

Sources with knowledge of Biden's deliberations said he is likely to recommend banning 100 types of assault weapons, restricting ammunition clips to 10 rounds and extending criminal background checks to private gun sales. He also may recommend that additional safeguards be created to prevent the mentally ill from buying guns.

Meanwhile, New York City Mayor Michael Bloomberg joined Maryland Gov. Martin O'Malley at a gun violence summit at Johns Hopkins University on Monday and called on the president to press for federal gun control measures, including an assault rifle ban and limits on ammo magazines. O'Malley outlined his own plan to seek additional restrictions on gun sales in Maryland.

Any gun control measure faces stiff opposition in the Republican-controlled House. And while the school shooting in Connecticut convinced some pro-gun lawmakers to call for additional safeguards to protect children, some of them, including Sen. Joe Manchin, D-W.Va., are skittish about backing anything as drastic as a ban on some types of guns.

And Sen. Majority Leader Harry Reid, D-Nev., also may be wary of pushing a gun ban at a time when 20 Democratic Senate seats will be up in the 2014 elections, many of them in pro-gun states.

Congress last passed a ban on assault-style weapons in 1996, but let it lapse a decade later.

The White House alarmed congressional Republicans with claims that Obama could enact some gun measures by executive order, without congressional approval. Rep. Steve Stockman, R-Texas, went so far as to threaten to press for impeachment if Obama acted on his own.

Gun rights advocates are pushing their own legislation.

Mike Hammond, legal counsel for Gun Owners of America, said his group drafted legislation, introduced by Stockman, that would repeal a federal law banning guns in school zones, which proponents said would deter potential attackers form targeting schools.

Before meeting with Obama, Biden held a final round-table discussion Monday with Attorney General Eric Holder, Homeland Security Secretary Janet Napolitano and Health and Human Services Secretary Kathleen Sebelius. The meeting also included a group of Democrats who are members of the congressional Gun Violence Prevention Task Force.

The task force's chairman, Rep. Mike Thompson, D-Calif., said the group would release its own proposals in February.

"Meaningful progress toward reducing and preventing gun violence cannot be made by just one branch of government," Thompson said Monday.