Democrats in the U.S. Senate succeeded in blocking a bill that would have cracked down on Syrian and Iraqi refugees coming to the United States as the measure became a referendum for Republican presidential candidate Donald Trump.

Senate Democrats were seeking to force an election-year vote on the issue as Trump has advocated barring Muslims from entering the U.S.

The measure was voted 55-43, short of the needed three-fifths vote to move ahead, according to the Associated Press.

The House version of the bill would require new FBI background checks and individual sign-offs from three high-ranking federal officials before any refugee from Syria or Iraq is allowed to enter the U.S.

The American Security Against Foreign Enemies Act was passed in the House last November after the Paris terrorist attacks, getting 289 votes, a veto-proof margin despite opposition from President Barack Obama.

Democrat leader Sen. Harry Reid said, "This bill is just another step in the absolute wrong direction, the direction of Donald Trump. The Democrats are committed to opposing the hateful views of Trump and his Republican enablers."

Senate Republicans who supported the bill said it is difficult to check immigrants from Syria and Iraq because of poor or non-existent record keeping.

"So it is any wonder that the citizens we represent are concerned?" said Senate Majority Leader Mitch McConnell. "No wonder dozens of Democrats joined with Republicans to pass this balanced bill with a veto-proof majority over in the House."

Republican presidential candidates Ted Cruz of Texas, Marco Rubio of Florida and Rand Paul of Kentucky left campaign and returned to Washington to vote for the measure.

Democratic presidential candidate Bernie Sanders of Vermont and Republican Sen. Lindsey Graham of South Carolina missed the vote.

The report said opposing the bill may put Democrats in a tight spot in rejecting a measure that many consider as reasonable anti-terror bill.

Reid said Democrats wanted to propose an increase in anti-terrorism fund for local police forces and airport security and banning the sale of guns and explosives to people on federal terrorism watch lists.

Reid said the House bill "scapegoats refugees who are fleeing war and torture instead of creating real solutions to keep Americans safe."

House Speaker Paul Ryan said the bill is a security test, not a religious one.

While Republicans said the measure does not have religious tests, Cruz and Jeb Bush have suggested giving preferences to Christians.

Obama told politicians in November that they were raising worries over refugees.

"Apparently, they're scared of widows and orphans coming into the United States of America," Obama quipped.