Iran will present new proposals at talks on Saturday aimed at easing concerns about its nuclear activity, state television said, but it was unclear if Tehran was willing to address its disputed uranium enrichment drive as six world powers want.

It was the latest apparent attempt to strengthen Iran's position ahead of the talks, which the powers insists must tackle higher-grade enrichment by Tehran seen in the West as a disguised bid to develop the means to make nuclear weapons.

The Islamic Republic says it is refining uranium solely for electricity and medical treatments. Western states do not believe this and the United States and Israel have not ruled out military action if diplomacy fails to curb Iran's nuclear work.

Iran's representatives will participate in the negotiations with new initiatives and we hope that the (six powers) will also enter talks with constructive approaches, said the head of Iran's Supreme National Security Council, Saeed Jalili, according to Iran's English-language Press TV on Wednesday.

Jalili, Iran's chief nuclear negotiator, said it was ready to hold progressive and successful talks on cooperation but that the language of threat and pressure against the Iranian nation has never yielded results.

Previous rounds of talks with the P5+1 group of countries - comprising the United States, Britain, France, Russia, China and Germany - foundered in part because of Iran's refusal to negotiate on the scope of its enrichment work, instead floating vague proposals for trade and security cooperation.

In February Jalili wrote to Catherine Ashton, the European Union's foreign policy chief and lead representative of the powers, saying Iran would put forward new initiatives in any future talks but did not spell out what they were.

SUSPENSION OF HIGHER-GRADE ENRICHMENT?

On Monday, the head of Iran's Atomic Energy Organisation, Fereydoon Abbasi-Davani, raised the possibility of Iran suspending enrichment to the 20 percent level of fissile purity if its needs were met.

The proposal did not address Western concerns about what would ultimately happen to Iran's existing reserve of higher-grade enrichment uranium.

Uranium needs to be refined only to the 5 percent level for use in running power plants. A 90 percent threshold is required for atomic bomb material.

Iran says it needs a 20 percent stockpile to fuel a medical isotope reactor. Western powers fear Iran's underlying goal is to advance towards bomb-grade purity and seek international guarantees via negotiations that this will not come to pass.

Alongside the outwardly cooperative tones, Iran has kept up some tough rhetoric. On a visit to Iran's Gulf coast, President Mahmoud Ahmadinejad warned Western powers that the Islamic Republic would not be bullied during the talks in Istanbul.

They constantly insult the Iranian nation and use a language of force against Iranians, the state news agency IRNA quoted him as saying at a rally in the port of Bandar Lengeh.

Speaking on behalf of the Iranian nation, I tell them that this method will not work ... and that they should speak with respect.

If progress is made, the talks could pave the way for an easing of increasingly crippling international sanctions imposed on Iran over the nuclear dispute and might lift the threat of Israel attacking the atomic sites of its arch-enemy.

Western countries hope the sanctions pressure will squeeze nuclear concessions from Tehran. But a Western diplomat said earlier this week that hopes for Saturday's talks were modest and at best they would lead to a second meeting.

Iran state says it has a sovereign right to uranium enrichment under terms of the nuclear Non-Proliferation Treaty. It accuses the nuclear-armed West of hypocrisy and of trying to stifle its technological progress.

(Editing by Mark Heinrich)