HARTFORD, CONN. — With time running out on the chance to pass gun control legislation, President Barack Obama on Monday warned Congress not to use delaying 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.

“The day Newtown happened was the toughest day of my presidency,” Obama said in an emotional speech from Connecticut’s capital. “But I’ve got to tell you, if we don’t respond to this, that’ll be a tough day for me too.”

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 brought 12 family members back to Air Force One for the trip back to Washington. The relatives want to meet with senators who’ve yet to back the legislation to encourage their support in memory of their loved ones.

“Nothing’s going to be more important in making sure that the Congress moves forward this week than hearing from them,” Obama said. His eyes teared as he described Nicole Hockley, who lost her 6-year-old son, Dylan, saying how she asks him every night to come to her in her dreams so she can see him again.

“If there’s even one thing we can do to prevent a father from having to bury his child, isn’t that worth fighting for?” Obama asked.

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.”