DUBAI/VIENNA (Reuters) - Iranian President Hassan Rouhani said on Saturday new U.S. sanctions were against the spirit of Tehran's nuclear negotiations with world powers, but added he was not pessimistic about the talks continuing.

The United States on Friday penalized a number of Iranian and other foreign companies, banks and airlines for violating sanctions against Tehran largely tied to a decade-old dispute about its nuclear programme.

Washington said it was sending a signal that there should be no evasion of the sanctions while international talks continue on relaxing them if Iran agrees to curb its nuclear activities.

Asked for his reaction to the U.S. moves, Rouhani said at a news conference in Tehran: "They are in conflict with the spirit of talks. They are unconstructive in my opinion."

In remarks quoted by the state news agency IRNA, Foreign Ministry spokeswoman Marzieh Afkham said such actions "put into question the seriousness, honesty and good faith of negotiations with the U.S."

However Rouhani also struck a more positive tone later in the news conference, suggesting there was hope of reaching a deal by the November 24 deadline.

"It is tough but I'm not pessimistic about the continuation of the talks," he said.

"Our nuclear negotiating team should not feel alone. The Iranian nation, leader and my government are behind them."

Iran and the United States, France, Germany, Britain, China and Russia failed to meet a July 20 deadline to negotiate a comprehensive agreement under which Iran would curb its nuclear activities in exchange for the easing of economic sanctions that have crippled its economy.

The new deadline was extended to Nov. 24. Members from all parties are set to meet on the sidelines of the UN general assembly in New York, Rouhani said.


DEADLINE

The U.S. move came after diplomats in Vienna said Iran had apparently failed to meet an Aug. 25 deadline to answer questions from the U.N. International Atomic Energy Agency (IAEA) about suspected nuclear bomb research. Iran denies any such activity.

The diplomatic sources said contacts between the U.N. watchdog and Iran were believed to be continuing and it was still possible Tehran could provide information to the U.N. agency in time to influence the findings of a closely-watched quarterly IAEA report. The sources spoke before the U.S. sanctions were announced.

The IAEA, which regularly inspects Iran's nuclear facilities, is expected to issue a report on the country's nuclear programme around Sept. 3.

The new U.S. sanctions have direct relevance for the IAEA's long-stalled probe, as the U.S. State Department said one of the entities targeted was the Organisation of Defensive Innovation and Research (SPND), which it said was "primarily responsible for research in the field of nuclear weapons development".

It said the Tehran-based SPND, mentioned in an IAEA report in 2011, was founded by Mohsen Fakhrizadeh.

Western officials and experts think the shadowy military figure played a pivotal role in suspected Iranian work in the past to develop the means to assemble a nuclear warhead behind the facade of a declared civilian uranium enrichment programme.

They say shedding light on his alleged activities is critical to understanding how far Iran advanced then and to ensuring they are not continuing now, something the West wants any diplomatic deal with the Islamic Republic to guarantee.

While dismissing the allegations of a nuclear weapons agenda as fabricated by its foes, Iran has pledged to cooperate with the IAEA since Rouhani was elected president in 2013.


(Editing by William Maclean and Andrew Roche)