Supporters of equal marriage in the US state of Illinois have launched a $2 million (£1.3 million) campaign to legalise equal marriage in the state.

Illinois Unites for Marriage is a human rights group which advocates for equal marriage, and represents civil rights and political groups.

In a release on Tuesday, the group said it would place 15 field organisers throughout the state in order to engage equal marriage supporters, and that it planned to target legislators in opposition to the lifting of a state-wide ban on same-sex marriage.

Richard Carlbom, director of state campaigns at Freedom to Marry, said: “It’s a new day in Illinois, with a fresh strategy to bring the freedom to marry to all loving and committed couples in the state. In the wake of historic rulings for marriage at the Supreme Court, Freedom to Marry and our partners are re-energized for this new phase of the campaign, and more committed than ever to following through for the win. With smart mobilization at Illinois Unites and continued leadership in the Legislature, we’ll make Illinois the next marriage state this session.”

The Illinois Senate passed a bill to remove the ban in February, but the bill’s sponsor in the House did not call it for a vote, as he said it did not have enough votes to pass.

Last month, opponents to equal marriage in the US state of Illinois celebrated the fact that the bill to legalise same-sex unions never went to a vote.

Jim Bennet is the chairman of the coalition, and he said that the next few months are critical to the cause, as lawmakers should take up the bill again in autumn.

The bill’s sponsor Greg Harris wept as he announced that, due to a lack of support, the bill would not be voted on. Mr Harris said he planned to lobby for the bill before the next legislative session in the autumn.

Opponents to the bill may be calling “victory” prematurely however, as Mike Madigan, House Speaker extended the deadline for the bill to August 31, allowing it a new potential lease of life, if its advocates can gather support before then.

Lawmakers in the US state of Illinois also wrote an open letter apologising to advocates of equal marriage in the state as the bill failed to be called for a vote, despite passing in the Senate on Valentine’s Day.

Nine US states, and Washington DC currently allow equal marriage, and it will become law in Rhode Island, Delaware and Minnesota in the summer.

The US state of Maryland in November 2012 became the first state to legalise equal marriage by means of a popular vote back in 2012. The law came into effect on 1 January 2013.

Washington and Maine also legalised equal marriage in referendums in those states on the same day.

The US Supreme Court is expected to rule on two cases surround equal marriage, in the next two weeks, potentially making a groundbreaking ruling for equal marriage in the state of California, and the whole of the US.