WASHINGTON - The United States on Monday greeted the official launch of the Iran-Pakistan natural gas pipeline project with fresh warnings that it could trigger US sanctions against Pakistan.

“We have serious concerns if this project actually goes forward that the Iran Sanctions Act would be triggered,” State Department spokesperson Victoria Nuland said.

The spokesperson was responding to a Pakistani journalist's question at the daily Press briefing whether she would like to allay fears of the sanctions as the stock market in Karachi had crashed following the project's inauguration.

"I would not like to allay those fears," Nuland said grimly.

“We've been straight up with the Pakistanis about these concerns. And as I said at some length last week, we are also working very closely bilaterally to support alternative projects to provide Pakistan with the energy that it needs,” Nuland added.

Iranian President Mahmoud Ahmadinejad and Pakistani President Asif Ali Zardari held a groundbreaking ceremony in Iran for construction to extend the pipeline into Pakistan.

But American media reports said there were major doubts about how Pakistan will provide the $1.5 billion needed to construct the pipeline, and Nuland expressed some skepticism that the project would proceed.

“We've heard this pipeline announced about 10 or 15 times before in the past. So we have to see what actually happens,” Nuland said.

“This pipeline project, if it actually goes forward – we've seen that promise many times – would take Pakistan in the wrong direction right at a time that we're trying to work with Pakistan on better, more reliable ways to meet its energy needs,” she said.