Updated 10:44pm – The Illinois Senate has approved a bill to legalise same-sex marriage – although it still has to pass the House before it becomes law.

On Thursday – Valentine’s Day – the Senate, which is controlled by the Democrats, voted 34-21 to approve the measure.

However, House Republican Leader Tom Cross said he was not sure whether it would gain Republican support.

There also was concern that some black Democratic legislators from Chicago, President Obama’s home city, could oppose the measure because of pressure from African-American Christian pastors.

Meanwhile, Reuters reports two Democratic state lawmakers broke with their party leaders on Thursday and introduced measures in both chambers of the legislature that call for an amendment to the state constitution to enshrine marriage as between a man and a woman.

Yet the bill’s sponsor, Senator Heather Steans, told the Associated Press it was “a vote for the history books.”

“We have the opportunity today to welcome all families in Illinois as equally valued,” she said.

Governor Pat Quinn, a Democrat, already indicated he would sign the bill into law.

Earlier this month, Governor Quinn said that “marriage equality is a matter of fairness and equal rights under law.”

“We took the first step towards marriage equality two years ago when I signed civil unions into law,” he said. Since that day, thousands of committed couples in 92 counties across our state have entered into civil unions,” adding. “Now is the time for the next step in providing equal rights to all people in Illinois.

Earlier this month, the bill passed the Illinois Senate Executive Committee.

The Senate attached an amendment before passing the legislation which states no church or religious organisation would be forced to perform same-sex marriages.

It also said that churches could not be sued if they did not allow parishes to be used for equal marriage ceremonies.