Prime minister during Iran's 1980-88 war with Iraq, Mousavi, 67, is seriously considered by many moderates and even some conservatives as their main presidential candidate and a strong rival to President Mahmoud Ahmadinejad in June's election.
"No one in Iran would accept suspension," he was quoted as telling the paper on its website.
Iran, the world's fourth-largest oil producer, says its nuclear programme is aimed at generating electricity and not covertly building nuclear weapons, as the West suspects. It has repeatedly ruled out halting its enrichment programme.
However, chief nuclear negotiator Saeed Jalili was quoted as saying on Monday that Iran would welcome constructive dialogue with six world powers, including the United States.
The Obama administration has offered a "new beginning" of diplomatic engagement if Iran "unclenches its fist".
Mousavi told the FT a solution to the nuclear dispute did not only depend on Tehran. "It will also depend on the discourse the Americans use and the issues they pursue. The more realistic they become and recognise Iran in this issue, naturally the better the ground will be prepared to find solutions.
"No one will retreat. But we have to see what solutions or in other words what guarantees can be found to verify the non-diversion of the programme into nuclear weapons," the paper's website quoted him as saying.
A solution could be reached by "technical negotiations".
ECONOMIC PRIORITIES
When he was prime minister, Mousavi, who has stayed away from politics and the public eye in the past 20 years, defended a state-controlled economy, although he told a news conference this month Iran needed privatisation, the creation of jobs and foreign investment.
He told the FT he believed in the "strong presence of the private sector", adding his economic priorities were "inflation, unemployment and the improvement of business".
Ahmadinejad is criticised by reformists and even some of his conservative backers for his economic policies, blamed for fuelling inflation, which reached a peak of nearly 30 percent last year, and wasting petro-dollars.
Inflation would be curbed "through monetary policies, imports, making the private sector active and increasing production", the paper quoted Mousavi as saying.
He said subsidies should be targeted. "The most important one is the energy subsidy and we have to gradually work on it," he said, saying it could probably be achieved in 10 years.
He also said he would consider restricting imports.
"I have to see which sections should be restricted and over what period of time," he was quoted as saying.
"We have gone too far in opening up to imports. This has to be revised. We have to take bigger steps to support our national economy." (Writing by Alison Williams; Editing by Jeremy Laurence)
