NEW YORK, May 15 (Reuters) - A federal judge has refused to toss Chevron's lawsuit against a New York attorney and others who helped secure an $18 billion damages award against the U.S. oil giant over pollution in Ecuador's Amazon jungle.

U.S. District Judge Lewis Kaplan on Monday upheld most of Chevron's racketeering case against the attorney, Steven Donziger, a group of Ecuadorians and environmental groups, finding that "Chevron's extortion allegations are more than sufficient" for the case to proceed.

Kaplan, however, called Chevron's accusations of unjust enrichment "premature at best" since Donziger and the other defendants have not yet touched the $18 billion award.

Chevron sued Donziger, environmental groups and some of the Ecuadorians under the Racketeer Influenced and Corrupt Organizations Act, accusing them of orchestrating a campaign of intimidation and extortion.

Donziger and the defendants have claimed the lawsuit is a Chevron tactic to avoid paying the pollution award.

Kaplan on Monday, in a separate ruling, denied a request by Chevron to attach the assets of Donziger and the Ecuadorians in anticipation of a recovery of the damages award.

The case is Chevron Corp v. Steven Donziger et al, U.S. District Court for the Southern District of New York, No. 11-0691.

For Chevron: Randy Mastro of Gibson, Dunn & Crutcher in New York.

For Donziger: Jon Keker of Keker & Van Nest in San Francisco.

(Reporting By Basil Katz)

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