By Jeremy Laurence
SEOUL (Reuters) - A senior U.S. official on Monday said the situation over Iran's nuclear program was becoming increasingly worrying and an urgent diplomatic solution needs to be found.
The United States and Israel have not ruled out military action against Iran's nuclear facilities if diplomacy fails to resolve a dispute over a program they suspect is aimed at developing atomic weapons.
Iran denies it is seeking nuclear weapons and says it would respond to any strike by attacking Israel and U.S. interests in the Gulf.
"Iran is violating international obligations and norms. It is becoming a pariah state," Robert Einhorn, the State Department senior adviser for non-proliferation and arms control, told a news conference in the South Korean capital.
"The situation in Iran has become more and more worrisome. The timeline for its nuclear program is beginning to get shorter, so it is important we take these strong steps on an urgent basis.
"If we do not, pressures will grow for much stronger actions. The U.S. favours a diplomatic solution pressure, but if we cannot achieve a diplomatic solution soon, inevitably interests will grow in a different kind of solution. That is why we need to act soon."
Iran's nuclear ambitions, its claim to have shot down a U.S. spy drone in its airspace on Sunday and last week's storming of the British embassy in Tehran by protesters has contributed to a sharp increase in tensions in the region.
He said enforcing sanctions would force Iran to negotiate seriously.
Western nations last week significantly tightened sanctions against Iran, with the European Union expanding an Iranian blacklist and the Senate passing a measure that could severely disrupt Iran's oil income.
Einhorn said the latest round of sanctions do not include crude oil imports, crucial to energy-starved economies like South Korea.
"But we discourage countries from continuing to import crude oil in large quantities," added Einhorn, acknowledging that at the present time "pressure was tight" on the oil market.
"We are conscious of energy security needs of countries like the Republic of Korea and don't want to interfere with those needs," he said, of Asia's fourth largest economy.
Einhorn said he had received a positive response during talks with South Korean officials about tightening sanctions, adding Seoul was considering what additional measures to take.
(Reporting by Jeremy Laurence, Editing by Jonathan Thatcher)