Looking for His glorious appearing! Titus 2:13

VIENNA (Reuters) - Major powers appear to have made only limited headway in making sure Iran will not be able to build an atomic bomb any time soon, underlining the uphill task they face after talks that began in February were extended by four months.

Western officials say some progress was achieved during the most recent round of negotiations with Iran - enough to justify continuing the high-stakes diplomacy.

Crucially, they said they believe Iran's negotiators genuinely want to reach an agreement in order to win relief from sanctions that have severely damaged its oil-dependent economy, rather than trying to gain more time for nuclear advances.

"I am convinced that they are committed," a senior Western diplomat said, after Iran and the six world powers failed to meet a self-imposed July 20 deadline for a comprehensive accord and decided to prolong the talks until late November.

But it is unclear to what extent that is shared by Supreme Leader Ayatollah Ali Khamenei, who wants an end to sanctions but is seen as wary of a detente with the West.

On the most contentious issue in the decade-old standoff - Iran's capacity to make nuclear fuel that has military uses as well as the civilian ones Tehran argues for - positions remain far apart.

The United States, France, Germany, Russia, China and Britain want Iran to scale back its nuclear program. Iran says it is entirely peaceful and wants sanctions lifted quickly.

"We still have a considerable way to go," a U.S. administration official said.