June 24 (Reuters) - U.S. Democratic presidential candidate Barack Obama has offered new steps to crack down on speculation in oil markets, saying his plan would help rein in runaway fuel costs.

A jump in gasoline prices above $4 a gallon has spurred consumer anger and is a major theme in the race between Obama and his Republican rival in the November election, John McCain.

McCain, an Arizona senator, has also expressed concern about oil-market speculation and has called for investigating cases of abuses as well as overhauling regulations for the trading of futures contracts in energy stocks, bonds and other instruments.

Here are some details of Obama's plan:

* The Illinois senator's campaign said he would close the so-called Enron loophole that exempts some energy speculators from U.S. regulations that apply to commodities traded over exchanges. It takes its name from the energy giant that benefited from the law and later collapsed because of massive accounting fraud.

* His plan would require U.S. energy futures to trade on regulated exchanges.

* Obama is calling for more data on index funds and other similar types of investments to boost transparency of institutional players in commodities markets.

* He backs legislation that would direct the Commodity Futures Trading Commission to investigate proposals such as increasing margin requirements in the market.

* He would aim to stop energy traders from evading U.S. regulations by conducting transactions through foreign subsidiaries of U.S. exchanges.

* He would call on the Federal Trade Commission to expedite investigations of suspected price manipulation and direct the Justice Department to look at whether illegal activity has contributed to the run-up in oil prices. (Writing by Caren Bohan and Paul Grant)