US plans for a possible military strike on Iran are ready and the option is “fully available”, a US diplomat said, days before Tehran resumes talks with world powers which suspect it of seeking to develop nuclear arms.

The United States has said it considers military force a last resort to prevent Iran using its uranium enrichment to make a bomb. Iran insists its nuclear program is for purely civilian purposes.

“It would be preferable to resolve this diplomatically and through the use of pressure than to use military force,” Ambassador Dan Shapiro said in remarks broadcast Thursday.

“But that doesn’t mean that option is not fully available – not just available, but it’s ready. The necessary planning has been done to ensure that it’s ready,” said Shapiro.

The United States, Britain, France, Russia, China and Germany have been using sanctions and negotiations to try to persuade Iran to curb its uranium enrichment, which can produce fuel for reactors, medical isotopes, and, at higher levels of purification, fissile material for warheads.

Meanwhile, Tehran’s chief nuclear negotiator said Thursday ahead of crunch talks with world powers in Baghdad next week that Iran rejected Western pressures over its nuclear activities and said will never give up its rights.

“If we participate in the negotiations... it is because of our resistance (to Western powers). Thanks to our resistance, we have defended the rights of the Iranian people,” Saeed Jalili said in a speech broadcast on local television.

“The Iranian people will never give up even an iota of their rights,” Jalili added, in reference to Tehran’s nuclear drive which the West suspects is masking a weapons program. Tehran vehemently denies the charge. After a 15 month hiatus, Iran and the P5+1 powers - Britain, China, France, Russia and the United States plus Germany - held their first talks in Istanbul in mid-April, which were described as “positive.”

US President Barack Obama warned Iran in March that time was running out to resolve the standoff through diplomacy.

But Jalili was defiant on Thursday, insisting that sanctions and international pressure were not affecting Iran’s determination.

“Those who think they can pressure Iran with these sanctions are wrong... because the sanctions have allowed us to make progress,” he said. He argued that the conditions imposed on Iran at talks in Geneva in 2009 for the delivery of uranium enriched to 20 percent for its Tehran research reactor had in fact forced it to produce the nuclear fuel itself.

“We told them: ‘If you do not give us the fuel, we will produce it ourselves.’ I will never forget the smiles from certain members of the P5+1. But in less than two years we produced the fuel, and we are using it today.”

Iran currently enriches uranium to 3.5 percent and to 20 percent. The former it says is to power its Bushehr nuclear electricity plant and the latter it says is to generate medical isotopes in its Tehran research reactor.