By the BBC's Tom Brook

Celebrated American TV writer and producer Steven Bochco is taking one of his biggest gambles with the launch this weekend of a black CBS TV drama series called City of Angels.

Bochco, whose credits include Hill Street Blues and NYPD Blue, knows the odds are against him. Several efforts in the past to create a successful black TV drama series have failed because white audiences in America have stayed away.

City of Angels stars Blair Underwood and Vivica A Fox in a medical drama that revolves around the Angels of Mercy Hospital in inner-city Los Angeles.

Most of the cast is either black or Hispanic, and, for the first-time in a network drama, so is the majority of the crew. The show's co-creator Nicholas Wootton confirmed that more than 70% of the crew is made up of racial minorities and women - far higher than most TV series.

Pressure for reform

City of Angels arrives on American TV screens in the wake of strong criticism of the TV networks from the National Association for the Advancement of Coloured People (NAACP).

The group is outraged that the networks have done so little to employ African-Americans both on and off screen.

Last summer the NAACP's persuasive president, Kweisi Mfume, threatened a viewer boycott as he began to escalate a campaign to bring about change. The NAACP's main complaint was that none of the network's new autumn shows featured a black or Hispanic actor in a leading role.

Steven Bochco says he began plans to create a black drama well before the NAACP criticism. He hopes his new series will succeed not by making race central to the story but by creating a compelling medical drama that stands on its own, driven by life and death issues.

Bochco believes that previous efforts at black drama foundered because they focused too much on the experience of being African-American.

Minority watchdog groups are eagerly awaiting the launch of City of Angels, although they remain anxious about the series failing. The stakes are high.

If there is no audience it is feared it will only confirm the prevailing view among TV executives that hour long drama series dealing with race can never succeed.

Policy review

By contrast half-hour American comedy shows with black actors like The Cosby Show and The Jeffersons have generally found it much easier to win support from mainstream audiences.

But the morale of groups campaigning for more inclusive and diversified programmes has been buoyed this month by agreements from some of the broadcast networks in the past few days.

NBC was the first to initiate a new policy on 5 January when it announced it would aim "for the full inclusion of people of colour in employment, casting and image portrayal".

This move was seen as a major victory for the NAACP's campaign. NBC's president Bob Wright said the network will launch a number of "aggressive initiatives" to ensure the new policy is implemented.

Among them is a plan to sponsor a "diversity seminar" next month for TV producers and studio heads where representatives from the NAACP will be present.

Although some minority groups welcomed this movie John Ridley, a writer for NBC's Third Watch was insulted.

He wrote to the New York Times to say: "It's almost sad that the networks have agreed to stage a diversity day for its executives to explain how to go about hiring minority employees, as if it were some weird science."

Cost of failure

But Paris Barclay, the co-executive producer of City of Angels, is impressed that the new network policies stipulate that fresh shows hire minority writers.

He sees this as a real breakthrough, because nowadays it is writers like David E Kelley (Ally McBeal, The Practice), David Chase (The Sopranos) and Dick Wolf (Law & Order) who have the most power to shape the content of network TV.

Bochco and his collaborators are hoping that City of Angels can transcend American viewer apartheid and break down the strong barriers that have so far prevented black and white audiences from enjoying the same programmes.

If the show succeeds its supporters believe it will do far more to bring diversity to American TV drama than any of the new network guidelines.

They will be anxiously awaiting the release of viewing figures after the first episode of City of Angels is broadcast on Sunday night.