President Obama with Nicole and Ian Hockley, who  lost a child at the Sandy Hook school shooting. (Photo: AP Photo/Susan Walsh)

HARTFORD, Conn. (AP) — With time running out on the chance to pass gun control legislation, President Barack Obama on Monday warned Congress not to use delay tactics against tighter regulations and told families of the Sandy Hook Elementary School shooting victims that he's "determined as ever" to honor their children with tougher laws.

Obama's gun control proposals have run into resistance on Capitol Hill, leaving their fate in doubt. Efforts by Senate Democrats to reach compromise with Republicans over expanding required federal background checks have yet to yield an agreement, and conservatives were promising to try blocking the Senate from even beginning debate on gun control legislation.

Some of the Sandy Hook families are making an attempt to push through the bill. Obama met with them privately before his speech at the University of Hartford Monday evening, then planned to bring 11 family members back to Washington aboard Air Force One. They want to meet with senators who've yet to back the legislation to encourage their support in memory of their loved ones.

"If you're an American who wants to do something to prevent more families from knowing the immeasurable anguish that these families know, now is the time to act," Obama said. "Now is the time to get engaged, to get involved, to push back on fear, frustration, and misinformation. Now is the time to make your voice heard from every state house to the corridors of Congress."

Obama argued that lawmakers have an obligation to the children killed and other victims of gun violence to allow an up-or-down vote in the Senate. That would require 50 votes to pass, rather than a procedural maneuver some Republican senators are threatening to require 60 votes, potentially sinking the legislation.

"Some back in Washington are already floating the idea that they might use political stunts to prevent votes on any of these reforms," Obama said told a packed gymnasium, with many wearing green ribbons in remembrance of the victims. "Think about that. They're not just saying they'll vote no on ideas that almost all Americans support. They're saying they won't allow any votes on them at all. They're saying your opinion doesn't matter. And that's not right."

Obama rode to the speech with Connecticut Gov. Dannel P. Malloy, who signed sweeping gun control legislation into law Thursday with the Sandy Hook families standing behind him.

"This week is the time for Congress to do the same," Obama said to a long standing ovation.

But legislation in Washington faces a tougher challenge, as the nation's memories of the shooting fade with time and the National Rifle Association wages a formidable campaign against Obama's proposals.

"I don't care about the NRA," Malloy said while Obama was meeting with the families.

Majority Leader Harry Reid brought gun control legislation to the Senate floor on Monday, though actual debate did not begin. He took the step after receiving a letter from 13 conservative Republican senators including Sen. Mike Lee, R-Utah, saying they would use delaying tactics to try preventing lawmakers from beginning to consider the measure. Such a move takes 60 votes to overcome, a difficult hurdle in the 100-member chamber.

The conservatives said the Democratic measure would violate the Second Amendment right to bear arms, citing "history's lesson that government cannot be in all places at all times, and history's warning about the oppression of a government that tries."

Echoing a frequent demand by Obama, Reid said that in the wake of December's killings of 20 first-graders and six educators in Newtown, Conn., Republicans should allow votes on gun control proposals including expanded background checks and bans on assault weapons, saying, "Shame on them."

He added, "The least Republicans owe the parents of those 20 little babies who were murdered at Sandy Hook is a thoughtful debate about whether stronger laws could have saved their little girls and boys."

Obama said the vote shouldn't be about his legacy, but about the families in Newtown who haven't moved on to other matters.

"Newtown, we want you to know that we're here with you," Obama said. "We will not walk away from the promises we've made. We are as determined as ever to do what must be done. In fact, I'm here to ask you to help me show that we can get it done. We're not forgetting."

A group of Sandy Hook families originally planned to travel to Washington earlier on Monday, but the White House offered to give the families a ride so they could also attend Obama's speech before their lobbying push.

The families' trip was organized by Sandy Hook Promise, a nonprofit started by community members in the wake of the shooting. "The group is encouraging senators to come together around legislative proposals that will both save lives and respect the Second Amendment rights of law-abiding Americans," the group said in a statement.

With time running out on negotiations, the White House is making an all-hands-on-deck push this week. Vice President Joe Biden and Attorney General Eric Holder planned to promote their plan at the White House on Tuesday with law enforcement officials. First lady Michelle Obama planned to wade into the debate Wednesday with a speech on youth violence in her hometown of Chicago. And on Thursday, Biden was taking part in a discussion on MSNBC's "Morning Joe" with people who have different views on gun control.

Organizing for Action, the grassroots group being formed out of Obama's re-election campaign to support his agenda, said it was launching online ads Monday asking the public to urge their senators to support background checks. The ads will target 11 senators — all Republicans — through Facebook and search engines. An OFA spokesman said the group was not disclosing the cost of the ad campaign.

Gun control is divisive in Newtown, Conn., as in the rest of the country. Not all Sandy Hook families support gun control, and even those involved with the lobbying push organized by Sandy Hook Promise are not backing the assault weapons ban. But those families are asking lawmakers to expand background checks, increase penalties for gun trafficking and limit the size of magazines.

Nicole Hockley, who lost her 6-year-old son, Dylan, introduced Obama and talked about the waves of sorrow that threatened to drown her in the past four months. But she also expressed her hope that this would be a moment for change. She said people are killed every day in America by gun violence, and addressing that shouldn't be a political issue.

"What law-abiding citizen, whether they are a gun owner or not, doesn't want to address this and save lives," she said.

Hockley and her husband, Ian, planned to fly on Air Force One along with:

— Mark and Jackie Barden — parents of 7-year-old Daniel

— Nelba Marquez-Greene — mother of 6-year-old Ana

— Neil Heslin — father of 6-year-old Jesse

— Jennifer Hensel — mother of 6-year-old Avielle

— Bill Sherlach — husband of Mary, a 56-year-old school psychologist

— Ben and Cheyanne Wyatt — parents of 6-year-old Allison

— David and Francine Wheeler — parents of 6-year-old Ben

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