US Senator Claire McCaskill of Missouri has announced her official support for equal marriage, and joined the increasing number on both sides of the political spectrum to endorse marriage equality.

The Democratic Senator took to her Tumblr page on Monday to write that she thought the US Government should extend equal marriage rights to all.

“I have come to the conclusion that our government should not limit the right to marry based on who you love,” she wrote. “While churches should never be required to conduct marriages outside of their religious beliefs, neither should the government tell people who they have a right to marry.”

She went on to write that her stance on the issue of equal marriage had “changed over time”.

“As many of my gay and lesbian friends, colleagues and staff embrace long term committed relationships, I find myself unable to look them in the eye without honestly confronting this uncomfortable inequality,” she wrote, adding that her decision is “simply the right thing to do,” she wrote.

“Good people disagree with me,” she wrote. “On the other hand, my children have a hard time understanding why this is even controversial. I think history will agree with my children.”

She went on to quote from the Bible verse 1 Corinthians 13, which reads: “And now abide faith, hope, love, these three; but the greatest of these is love.”

This official endorsement from the senator comes as the US Supreme Court is set this week to take up two cases challenging bans on equal marriage.

The Supreme Court will tomorrow begin to consider an appeal against The Defense of Marriage Act, urged on by President Obama and even Bill Clinton, the former President who signed DOMA into US law.

As well as the appeal on DOMA this month, the Supreme Court will also consider overturning Proposition 8, which bans same-sex marriage in California.

The former US Secretary of State Hillary Clinton, officially announced her support for equal marriage last week in a moving speech in which she called moves towards equality “breathtaking and inspiring”.

Republican Senator Rob Portman, who was among the original sponsors of the Defense of Marriage Act (DOMA), last week announced that he had changed his anti-equal marriage stance, citing his son’s coming out as part of his decision making process.

In February, Clint Eastwood joined over 100 top Republicans who signed up to argue that the Supreme Court should overturn Proposition 8.

In an interview, the United States House Speaker John Boehner said that he “can’t imagine” he would “ever” change from his current stance in opposition to equal marriage.

The head of a well-known law firm and top attorney said that he expects the US Supreme Court to resoundingly support equal marriage.

Senator McCaskill was recently sworn in for a second term, despite being considered a vulnerable Democrat. She was up against Todd Akin, who supported Don’t Ask Don’t Tell, and other controversial anti-gay bills. Senator McCaskill will be up for re-election in 2018.

The Supreme Court is expected to make rulings in both cases by the end of June.