Many US troops in Iraq were overjoyed to see President Barack Obama take his oath, but some were unhappy about one thing the Democrat has promised to do: permit gay and lesbian soldiers to serve openly.

Obama said during his campaign he opposed a 1993 law stating that homosexuals are not eligible to work in the US military, widely referred to as the "Don't Ask, Don't Tell" rule.

This month, Obama spokesman Robert Gibbs, when asked whether the new administration planned to scrap the law, replied on the president's transition website: "You don't hear politicians give a one-word answer much. But it's 'yes'."

But some of the 140,000 troops still in Iraq almost six years after the 2003 US-led invasion to topple Saddam Hussein appear uneasy about the prospect. Specialist Joseph Watson, from Texas, was "pretty excited" to see America's first black president sworn in, he said, after watching Obama's inauguration on a big TV screen at the dining hall of Forward Operating Base Prosperity, in Baghdad.

But the 30-year-old was a lot less excited about Obama's inclination to repeal the ban on gay men and women serving.

"Ah, I think that might cause a lot of problems," he said. "It's a big moral issue. It's giving the OK, saying that being gay is alright. Personally, I don't think being gay is OK."

Each year, the US military kicks out hundreds of soldiers for "homosexual conduct", although numbers have fallen from 1145 in 1998 to 627 in 2007, according to its own figures.

Many US soldiers hail from Republican-voting "Red States", where opposition to abortion and homosexuality runs deep and many are concerned that a Democratic administration means higher taxes, gay marriage and laws restricting gun ownership.

Even soldiers from "Blue", Democrat-leaning U.S. states often hold Christian values they say clash with Obama's proposal.

Specialist Justin Scharan, from Washington State, battled to contain a smirk on his reddening face when asked his view.

"I'm Christian, so I really don't believe it's a good thing. But if it happens, there's not much we can do," he said.

Obama opposed California's ban on gay marriage in November. He has said he supports equal legal rights for same-sex couples, a topic of vociferous debate between liberals and conservatives.

He is expected to reverse many of former President George W. Bush's policies, including by closing the US military's Guantanamo Bay detention centre, banning interrogation techniques seen as torture, and scrapping funding restrictions on stem cell research.

But he may be mindful of former President Bill Clinton's early days, when he failed to push through a change of policy on gays serving in the military and drew fire from Christian groups.

Some soldiers questioned on inauguration day in Iraq thought it would be the wrong time to bring up such a sensitive issue with the United States facing multiple crises, from wars in Iraq and Afghanistan to a US recession and global economic turmoil.

"I don't agree with it," said Staff Sargeant Tavar Cradle. "I think there's other, bigger issues that could be dealt with."

But one US soldier, who asked not to be named or identified by rank, said he agreed with Obama on gays.

"Put it this way: if they're willing to fight for their country, to me, it doesn't make a difference. Everybody has a right to defend their country, even if they are gay."