ISLAMABAD: Pakistan's president vowed to continue with a proposed pipeline project with Iran despite American warnings of sanctions, saying Islamabad's relations with Tehran would not "be undermined by international pressure of any kind."

Asif Ali Zardari made the comments alongside Iranian President Mahmoud Ahmadinejad, who is facing fresh Western pressure over his country's nuclear program.

Pakistan faces chronic energy shortages that feed anti-government anger, hobble industry and trigger unrest in an already poor country. The proposed pipeline would deliver natural gas from Iran to Pakistan, and go some ways to improving the situation.

But the U.S. wants Pakistan to halt the project because it would undercut international pressure to isolate Iran over its nuclear program. The issue is an irritant, though by no means the largest, in already badly strained relationship between Islamabad and Washington.

Iran maintains its nuclear program is entirely peaceful, but the U.S. and its allies worry the program is designed to ultimately deliver a nuclear weapon.

President Asif Ali Zardari was asked about the opposition to the pipeline project.

"Pakistan is lobbying the world, and our point of view is being accepted," he said. "Our bilateral relationships cannot be undermined by any international pressure of any kind."

In Washington, State Department spokeswoman Victoria Nuland said the U.S. was concerned about the pipeline, but noted the numerous "false starts and backing-and-forthing" that has occurred with the project.

"We've seen this discussion about this proposed pipeline go on for a long time, and there have been many fits and starts," she told reporters. "We think it's a bad idea. We've made that clear."

The pipeline project was first proposed in the 1990s, but has been plagued by delays.

Pakistan and Iran finalized the gas deal last year. Under the contract, Iran will export 760 million cubic feet (21.5 million cubic meters) of gas per day to Pakistan through a new pipeline beginning in 2014. The construction of the pipeline is estimated to cost some $7 billion.

Ahmadinejad didn't reference the nuclear program, but took a swipe at Washington, accusing it of being the cause of the problems in Afghanistan. The two-day conference, also attended by Afghan President Hamid Karzai, focused on Taliban peace talks and other regional issues.