WASHINGTON (AFP) - With a cast of TV news stars, deep pockets and an ambitious agenda, Al-Jazeera launches its US news channel on Tuesday, aiming to shake up the broadcast journalism market stateside.

The US cable channel will reach more than 40 million households and vastly expands the footprint of the Qatar-based media group, despite questions about how it will be received by American viewers.

Al-Jazeera America's audience is likely to start out small, but its bosses hope to have a big impact when it competes against already established brands such as CNN, MSNBC and Fox News.

Americans will be able to get 14 hours of news, documentary and discussion programming daily, and updates at the top of every hour 24 hours each day. But the selling point will be long-form reporting of stories overlooked by other news organisations.

"We know Americans want in-depth coverage of the news that matters to them," said Mr Ehab Al Shihabi, interim chief executive of Al-Jazeera America.

"They want more unbiased coverage and less opinion, that's what Al-Jazeera is about."

Yet some analysts say the channel will face a tough sell to US audiences because of its history in the Middle East, where it was the outlet for videos distributed by al-Qaeda and Osama bin Laden. Some conservatives claim it is still anti-Western.

Mr Shihabi said he believes Americans will come around once they see the programmes.

He said surveys indicate that "75 per cent of people who did not watch Al-Jazeera came on the negative size and 90 per cent of those who watch Al-Jazeera came on the positive side."

Mr Shihabi said 850 staff have been hired for 12 US bureaus, and will draw on 70 bureaus worldwide to give Al-Jazeera unmatched scale.

While the channel will be available to fewer than half of US households - notably absent from Time Warner Cable, which is in discussions on carrying Al-Jazeera - Mr Shihabi hopes to reach 100 per cent soon.

"We are investing heavily in advertising and branding," he said. "I'm sure it will be a short time before Al-Jazeera will be viral and people will be demanding Al-Jazeera." Since acquiring Current TV, a struggling US cable channel which nevertheless had reach to US homes, Al-Jazeera has brought in well-known names in the industry, such as Ms Soledad O'Brien and Mr Ali Velshi from CNN, and Ms Sheila MacVicar, formerly with ABC and CNN.

Al-Jazeera America president Ms Kate O'Brian said the channel will "stay away from pundits and crazy celebrity news" while "covering all the stories that need to be covered."

"Our success is how well we tell the stories," she said in a conference call with reporters. "We will get people talking about the channel and wanting the channel."

Along with 24-hour news, Al-Jazeera will include several showcase programmes starting with the 5:00 pm time slot and carrying into "prime time" evening viewing.

Mr Shihabi said the channel will have only six minutes of advertising per hour, compared with an average of 15 minutes for most other channels.

Al-Jazeera's US operation is headquartered in New York, with a vast news hub and studio across from Penn Station. In Washington, the channel has taken studio space formerly occupied by ABC at the Newseum, overlooking the US Capitol.

Mr David Shuster, a newly hired anchor and MSNBC and Fox News veteran, said he sees a "huge opportunity" because of the vast resources of Al-Jazeera, which he said probably becomes the largest broadcast news organisation in the world.

"It turns the news business on its head," Mr Shuster said. "People want to watch the news, they want to be taken to the scene of what is happening."

He said other cable news outlets have become politicised and that "rather than invest in the field they put talking heads out there who yell and scream at each other."

Ms Joie Chen, a former CNN and CBS journalist and one of the big US names lured to Al-Jazeera, said she was attracted by "the quality work they were doing."

"I wanted to be able to participate in the story telling. I did not want to be a news reader," said Ms Chen, who will host the channel's flagship US programme "America Tonight."

"We are not focused on the size of the audience, we are focused on the quality of the reporting.

"We want to tell stories that are currently underreported."

Former NBC news anchor Mr John Seigenthaler sees Al-Jazeera providing "a little more depth, a little more perspective, a little more context, what we are all looking for in journalism."

Mr Seigenthaler, the nightly news anchor, said the new channel will have notable advantages over other broadcasters.

"When I asked about ratings, they said they are not interested in ratings, they are interested in delivering the news. That's why this seemed like a different journey."