An equal marriage advocacy group in the US state of Illinois has announced that it is gearing up for a large-scale campaign to promote same-sex marriage ahead of the 2014 state election.

Civl rights group Equality Illinois has said that it will launch the $500,000 (£320,000) campaign to promote marriage equality.

The group says that half of the money will go towards voter education efforts, and that the second half will be used by the group’s political action committee, in order to fight opponents, reports the AP.

Equality Illinois also said that an organisation opposed to equal marriage had pledged $250,000 (£160,000) to oppose lawmakers, in particular Republicans, who supported equal marriage.

Earlier this 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 a week ago.

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.