Washington: In its bid to prevent Iran from developing nuclear weapons, US has warned Tehran against pursuing any such ambition. 

"President (Barack) Obama has long understood the regional and international consequences of Iran becoming a nuclear weapons’ state... That is why we are committed to prevent Iran from developing nuclear weapons," National Security Advisor Tom Donilon said.

"From his first days in office, he has made clear to Iran that it has a choice: it can act to restore the confidence of the international community in the purposes of its nuclear programme by fully complying with the IAEA and UN Security Council resolutions, or it can continue to shirk its international obligations, which will only increase its isolation and the consequences for the regime," he said in his address to the Washington Institute for Near East Policy.

"There is no escaping or evading that choice."

The National Security Advisor said Iran is facing sanctions that are far more comprehensive than ever before.

And "as a result it finds it hard to do business with any reputable bank internationally; to conduct transactions in Euros or dollars; to acquire insurance for its shipping; to gain new capital investment or technology infusions in its antiquated oil and natural gas infrastructure — and it has found in that critical sector, alone, close to USD 60 billion in projects have been put on hold or discontinued."

Leading multinational corporations understand the risk of doing business with Iran, and are choosing to no longer do so, he claimed. Some of these companies are: Shell, Toyota, Kia, Repsol, Deutsche Bank, UBS and Credit Suisse.

"The impact is real," he noted, adding that unless Iran complies with its obligations under the NPT and all relevant UN Security Council resolutions, the US will continue to ratchet up the pressure.

Donilon said the Iranian regime's nuclear programme is part of a larger pattern of destabilising activities throughout the region.

"So make no mistake, we have no illusions about the Iranian regime’s regional ambitions. We know that they will try to exploit this period of tumult and will remain vigilant. But we must also remember that Iran has many weaknesses and vulnerabilities," he said.

Externally, Iran's destabilising activities are backfiring by uniting its neighbours in the Gulf, he said.

The official said door to diplomacy remains open to Iran. "But that diplomacy must be meaningful and not a tactical attempt to ward off further sanctions. These choices remain available to the Iranian government."

"In the meantime, America and our partners will keep the pressure on by continuing our current sanctions efforts and seeking new lines of activity to target," Donilon said.