NEW YORK (Reuters) - A group of doctors and patients, some terminally ill, on Wednesday asked a New York court to rule that doctor-assisted suicide is not against state law.

The lawsuit, filed against New York Attorney General Eric Schneiderman in Manhattan Supreme Court, claimed that a New York law making it a crime to cause or aid another person to commit suicide does not apply to doctors who prescribe fatal drugs to mentally competent, terminally ill patients who ask for them.

Three of the doctors in the case - Timothy Quill, Samuel Klagsbrun and Howard Grossman - were also plaintiffs in a 1997 case before the U.S. Supreme Court challenging the New York assisted-suicide law under the U.S. Constitution. The Supreme Court ruled against them. All three have been prominent advocates for doctor-assisted suicide, which advocates prefer to call aid-in dying.

One of the patients in the lawsuit, Eric Seiff, 81, is a former Manhattan assistant district attorney who is being treated for cancer.

Seiff is not currently terminally ill, but the other two patients are. Sara Myers, 60, has amyotrophic lateral sclerosis, or Lou Gehrig's disease, and Steve Goldenberg, 55, has multiple HIV-related illnesses. Both told a news conference that they do not yet want to die but want to have the choice in the future.

Nurse and end-of life consultant Judith Schwarz, Charles Thornton, a Rochester, New York, neurologist, and non-profit End of Life Choices New York are also plaintiffs in the lawsuit.

The plaintiffs say in the lawsuit that the state's law against assisted suicide was never meant to apply to doctors helping mentally competent, terminally ill patients. They said helping such patients die was not assisted suicide but rather akin to withdrawing a patient from a ventilator.

Even if the law was meant to prohibit doctor-assisted suicide, they said, the court should rule that enforcing it violates patients' due process and equal protection rights under the state Constitution.

Besides Schneiderman, the lawsuit named the district attorneys of Westchester, Monroe, Saratoga, Bronx and New York counties, where the plaintiffs live or practice medicine.

Schneiderman's spokeswoman, Elizabeth DeBold, declined to comment.

Oregon, Washington and Vermont are currently the only states with laws explicitly allowing doctor-assisted suicide, and California's legislature is considering a similar law. A New Mexico judge has ruled in favor of doctor-assisted suicide, though the ruling is being appealed.

The case is Myers et al v. Schneiderman et al, New York Supreme Court, New York County.

(Reporting by Brendan Pierson; Editing by Ted Botha and Dan Grebler)