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The Arizona legislature has passed a bill requiring presidential candidates to submit birth certificates in order to get on the state's election ballot.

Republican Governor Jan Brewer can opt whether to sign the into law.

A lingering "birther" conspiracy theory asserts US President Barack Obama was not born in the US and is thus ineligible to hold the office.

The bill's Republican backers insist it is not aimed at Mr Obama. Arizona is the first to state to pass such a law.

The US constitution requires the president be a "natural born citizen", a clause widely interpreted to mean born in the US or in some cases to US citizens abroad.

Mr Obama has released a showing he was born in the US state of Hawaii, where officials vouch for its authenticity.

But the "birthers" claim Mr Obama was born in Kenya, his father's place of birth, or perhaps in Indonesia, where he spent several years as a child.

On Thursday, in rare remarks on the issue, Mr Obama dismissed the conspiracy theory, saying more people are worried about unemployment and fuel prices than his birth certificate.

Arizona is the first state in the nation to address the birther conspiracy with legislation, although the bill's Republican backers insisted it was not specifically aimed at Mr Obama.

'Integrity'

"It's essential that we bring back the integrity to the office," Republican State Representative Judy Burges said during debate.

The bill would require national political parties to submit affidavits affirming their presidential candidates are "natural born" citizens and to provide a "long form birth certificate" listing the name of the hospital and the attending physician.

If the candidate does not possess that document, the candidate can provide a baptismal or circumcision certificate, hospital birth record, mother's post-partum medical record or early census record.

Ms Brewer could opt either to sign the bill into law, to allow it to become law without her signature, or to veto it.

Democratic Representative Ruben Gallego voted against the bill and said he was embarrassed it had passed.

"Arizona is the first state to pass a birther bill," he told the Arizona Republic newspaper. "We look pretty much backward."

The birther conspiracy has simmered at the fringes of American politics since before the 2008 presidential election, despite repeated assertions by Hawaiian officials that Mr Obama's birth certificate plainly states he was born in the US state.

In August, a CNN found 11% of Americans believed Mr Obama was "definitely" born in another country and 16% "probably" born elsewhere. For Republicans, the numbers were 14% and 27%, respectively.

Real estate mogul and television personality Donald Trump has been promoting himself as a possible presidential candidate, in part by questioning Mr Obama's citizenship.

The move has vaulted Mr Trump to near the top of the polls of potential Republican presidential candidates, but has also been dismissed by political figures in Washington.

"I don't think he is really serious when we see a campaign launched on the birther issue," Republican House Majority Leader Eric Cantor said on Wednesday.