ANALYSIS-Sanctions tighten pressure on Iran's oil industry

* Companies with U.S. operations back away

* U.S. sanctions wide open to interpretation

* Some analysts say Iran can still find a way

By Simon Webb

DUBAI, July 14 (Reuters) - A new round of U.S. and European sanctions targets Iran's dilapidated oil sector from top to bottom, making it even more difficult to maintain output capacity and domestic supplies of fuel.

The United States, seeking to halt Tehran's nuclear enrichment activities, passed unilateral sanctions earlier this month that for the first time allow it to punish the U.S. operations of international firms who supply fuel to Iran.

Although the world's fifth-largest oil exporter, Iran lacks the refining capacity to meet domestic fuel demand and relies on imports to meet up to 40 percent of its gasoline needs.

The European Union's new measures are its first attack on technical assistance and investment in an oil industry already sapped by years of international isolation.