A Senate vote on tighter gun control laws is unlikely to occur next week, according to two Democratic sources, who described a hang-up among Republicans over bolstering rules regulating background checks during gun sales.

President Barack Obama has been pressing for new gun laws since December's shooting at a school in Connecticut. He will travel to Colorado Wednesday to resume his calls for laws he says would prevent the type of violence that left 26 people dead at Sandy Hook Elementary School.

Background checks have become the focus of federal legislation, and are regarded as the measure with the best possible chance of gaining congressional approval. Other provisions, including a ban on assault weapons and high capacity magazines, are not expected to gain enough support from Republicans and moderate Democrats.

Senate Majority Leader Harry Reid originally vowed to bring a gun control bill up for a vote when Congress returns from recess next week, but sources said Reid doesn't have the 60 votes needed to break a Republican filibuster of the legislation.

Democratic leaders are currently looking at ways to bring Republicans on board with their plan, which would require reworking the bill. Sources said Democrats would like to make a deal with Sen. Tom Coburn of Oklahoma, who could then convince other Republicans to support the plan.

Coburn has said that he'll oppose any measure bolstering background checks that includes record-keeping on gun owners.

Other opponents of increased background checks say the plan would unnecessarily apply to innocent handoffs between family members. Many say the current focus should be on improving the current system's record-keeping or insuring individuals with mental health issues are included in the database.

But proponents say the so-called gun show loophole means as many as 40% of gun sales are not subject to the type of background check which could keep firearms out of the hands of criminals.

Recent polling indicates a high level of support for requiring a background check on every gun sale. The most recent survey, from Morning Joe/Marist, found almost nine of ten Americans supported universal background checks. Other March surveys have put that number at 85 percent or above.

CNN Chief White House Correspondent Jessica Yellin contributed to this report.