MANILA (Reuters) - Philippines President Rodrigo Duterte has been rated "very good" in an opinion poll on his first 90 days in office, which has been defined largely by his deadly war on drugs and vitriol against Western leaders.

Only 11 percent of 1,200 Filipinos surveyed by the Social Weather Stations (SWS) agency said they were dissatisfied with his performance. That gave Duterte a net satisfaction rating of 64 percent, getting him off to a better start than predecessors Benigno Aquino, Joseph Estrada and Gloria Macapagal Arroyo, but short of the 66 percent achieved by Fidel Ramos in 1992.

The rating, announced on Thursday, was calculated by deducting the 11 percent from the 76 percent of respondents who said they were satisfied with Duterte's presidency, then rounding it off. Thirteen percent were undecided.

The SWS survey did not ask respondents to give a reason for the rating. It was conducted in face-to-face interviews held from Sept. 24-27, after Duterte had a spat with President Barack Obama over criticism of his anti-dugs campaign but before he said he was seeking new alliances with China and Russia.

A survey by Pulse Asia, another polling agency, less than a month after he took office on June 30 said Duterte had a record 91 percent trust rating. The two polls are not comparable.

Duterte won the May 9 election by a substantial margin after promising to expand a ruthless anti-crime campaign he started while mayor of Davao City, which had earned him nicknames like "the Punisher" and "Duterte Harry".

Political analyst Nelson Navarro said the SWS survey suggested Filipinos felt safer because Duterte had followed through with his promised war on crime and drugs, in which over 3,400 people have been killed.

He said Duterte's abrasive style and his sometimes profane outbursts against the United States, European Union and United Nations were not discrediting him either, and supporters would rally in his defense amid criticism at home and abroad.

"This is not going to be good manners and right conduct. What you see here is exactly what you get. His tough stance has gained him popularity across the Philippines," Navarro said.

"Everyone likes to dump on President Duterte for the extra-judicial killings but ... there is a kind of backlash on the perception of the West."

The SWS poll considers a net approval rating of over 70 percent as "excellent" and 50-69 percent as "very good".

(Reporting by Martin Petty; Editing by Raju Gopalakrishnan)