Environmental versus business interests faced off Thursday in the battle over the controversial Keystone XL pipeline, which would carry oil from Canada's tar sands to coastal Texas.

People worried about the environment and water in the most hotly contested area of the proposed pipeline, Nebraska's Sand Hills, pleaded for a halt to the $5.3 billion project at a public hearing attended by hundreds.

But supporters insisted that years of research have shown no harmful effects would come from the pipeline, and promised it would add much-needed jobs in a still sluggish US economy.

The US State Department is currently preparing its recommendation on whether to approve the project, and concluded in a draft report last month that it would have no major impact on the environment. A final decision rests with President Barack Obama.

"The main reason we oppose this pipeline is because it threatens our waters, which is the very livelihood of the landowners we're working with to protect their land," said Jane Kleeb, head of the Bold Nebraska Coalition.

"We expect that the State Department will finally hear us after four years to do a proper water study that still hasn't been done," Kleeb told a news conference ahead of the public hearing.

"The other thing that has not been done is a risk analysis on landowners' property. When a spill happens, what are those economic risks? Those two things we really want to see done and that's going to be the heart of many people's testimonies."

According to Vern Meier, vice president of pipeline safety and compliance at TransCanada, the company that would operate the pipeline, the project would not do any harm.

"Keystone will be a safe line, a link from Canadian and American oilfields to refineries on the US Gulf Coast," he said.

"It's our job to make sure that quality materials are used to construct it, that it's installed properly, that it's maintained to the highest standards."

Another TransCanada executive, Corey Courlet, said multiple studies have projected the same "minimal" effect.

"Four national environmental reviews in five years, 12,000 pages of documents all came to the same conclusion. Keystone XL will have minimal impact on the environment."

As the hearing got underway, a boisterous crowd filled an indoor auditorium, with attendees alternately cheering or booing speakers as they rose to voice their opinions.

Many of those opposed to the project wore baseball caps and shirts that said "Pipeline Fighter," while many of those who spoke in favor were dressed in business suits.

Often, when pro-pipeline people spoke, opponents in the audience raised their fists in silence.

"I am here today to tell you that we know how to build pipelines that are safe, efficient and reliable," said Tom Gross, director of Pipeline Oil and Gas distribution for the United Association of Plumbers and Pipefitters.

"Communities, states along the pipeline, will benefit from millions of dollars in tax revenues," he said.

The project aims to build an 1,980-mile (3,200-kilometer) conduit for oil from Canada's tar sands region to the US Gulf of Mexico coast.

TransCanada is already using a pipeline that came online in 2010 to serve refineries in Oklahoma and Illinois, and wants to increase its capacity from 590,000 to 1.4 million barrels per day by adding a second line -- Keystone XL -- along the northern route.

A Sioux Indian named Charlie Spotted Tail from South Dakota urged Obama to stick to promises he made when running for his first term in the White House.

"We need to challenge President Obama to stand by his 2008 call, to be the generation that finally frees America from the tyranny of oil," he said to a burst of applause.