The United States objected on Friday to a French court's planned release of a Lebanese leftist militant, saying he may still be a threat a quarter century after he was convicted of killing an American and an Israeli diplomat.

A French appeals court on Thursday granted conditional release to George Ibrahim Abdallah, imprisoned since 1984 and still in custody for now, contingent on his being deported to Lebanon, a step in the hands of the French Foreign Ministry.

"We don't think he should be released and we are continuing our consultations with the French government about it," State Department spokeswoman Victoria Nuland told reporters. "We have serious concerns that he could return to the battlefield."

The former head of the Lebanese Armed Revolutionary Brigade, Abdallah, 61, was sentenced to life imprisonment in 1987 for his role in the 1982 murders in Paris of U.S. military attache Charles Ray and Israeli diplomat Yacov Barsimantov, and the attempted murder of U.S. Consul General Robert Homme in Strasbourg in 1984.

A lower court granted Abdallah parole in November - prompting a rebuke from the U.S. ambassador to France, who said he deserved life imprisonment - and the prosecutors appealed.

In backing the November decision, the appeals court rejected prosecution warnings that he was still a threat. Abdallah, who made seven previous attempts to be released, won conditional liberty in 2003, but that decision was struck down on appeal.