By Fredrik Dahl and Mehrdad Balali
VIENNA/DUBAI (Reuters) - Iran has given a firm commitment to cooperate with a U.N. nuclear watchdog investigation into suspected atomic bomb research, the head of the agency said after what he described as a "useful" visit to Tehran on Sunday.
Yukiya Amano made the trip ahead of an Aug. 25 deadline for Iran to provide information relevant to the International Atomic Energy Agency's long-running inquiry into what it calls the possible military dimensions of the country's nuclear programme.
The issue is closely tied to Iran's negotiations with six world powers aimed at ending a decade-old standoff over its atomic activities and dispelling fears of a new Middle East war.
Iran denies its programme has any military objectives.
"This has been a short visit, but a useful one," Amano said in the Iranian capital after talks with President Hassan Rouhani and other senior Iranian officials, according to a statement issued by the IAEA in Vienna.
Referring to a phased cooperation pact agreed between Iran and the IAEA in November, Amano added: "I was very glad to hear from the highest levels a firm commitment to the implementation of the Framework for Cooperation, and to resolve all present and past issues through dialogue and cooperation with the IAEA."
The phrase "all present and past issues" refers in part to the IAEA's inquiry into alleged activities by Iran that could be relevant for developing a capability to build atomic bombs.
Since Rouhani was elected in mid-2013, Tehran has promised to work with the U.N. agency to clear up the suspicions about its nuclear programme.
But his eagerness to end the nuclear dispute as part of an effort to salvage the oil producer's sanctions-hit economy has been hampered by Islamic hardliners' opposition to any major concession to the West on the nuclear file.
After meeting Amano, Rouhani said on his English-language Twitter account that Iran was "determined to forge accord with the IAEA in the shortest possible time span. God willing, it can be done in less than a year."
Amano also met Foreign Minister Mohammad Javad Zarif, who leads Iran's negotiating team with the world powers - the United States, Britain, France, Germany, Russia and China.
With major gaps remaining over the permissible future scope of Iran's uranium enrichment programme - activity which can have both civilian and military uses - the talks between Iran and the six major states were last month extended until Nov. 24.
Under last year's Iran-IAEA transparency agreement, an attempt to jumpstart the long-stalled investigation, Iran agreed in May to implement five nuclear transparency measures by Aug. 25, two of which directly dealt with the nuclear bomb inquiry.
Diplomatic sources said in July that the IAEA was concerned about Iran's lack of engagement with the investigation.
They said there was still time for Iran to meet its commitments, noting that Tehran had occasionally waited until the last minute to make concessions in the past.
Amano's statement did not say whether specific progress was made during Sunday's talks, but that "officials on both sides have been able to plan how to move ahead with the existing practical measures, including the five measures" agreed in May.
He said the IAEA had proposed discussions on a number of new steps to be taken under the cooperation accord, adding: "I hope these can take place in the near future."
After years of what the West saw as Iranian stonewalling, Iran as a first step in May gave the IAEA information it had requested about its reasons for developing exploding bridge wire detonators. These can be used to set off an atomic explosive device but Iran says they are for civilian use.
Amano said Iran had provided explanations on its work related to the application of such detonators in the oil and gas industry "which is not inconsistent with specialised industry practices". He added, however, that the IAEA needed to assess all outstanding issues as "a whole" in a system.
The two issues Iran agreed to clarify by late August concern alleged work on explosives and computer studies related to calculating nuclear explosive yields.
They were among 12 specific areas listed in an IAEA report issued in 2011 with a trove of intelligence indicating a concerted weapons programme that was halted in 2003 - when Iran came under increased international pressure. The intelligence also suggested some activities may later have resumed.
(Editing by Alison Williams)