UPDATE 1-Oil cos pull workers, shut port ahead of Ida

* Fast-moving Hurricane Ida strengthens

* Louisiana Offshore Oil Port stops tanker offloading

* Chevron, Anadarko evacuating workers, no output shut (Adds Chevron, Anadarko evacuating workers, Conoco operations normal, byline)

By Erwin Seba

HOUSTON, Nov 8 (Reuters) - Fast-moving, strengthening Hurricane Ida led oil companies to begin evacuating workers on Sunday from the Gulf of Mexico and prompted the nation's only offshore oil port to stop taking foreign crude from tankers.

Chevron Corp (CVX.N) and Anadarko Petroleum Corp (APC.N) said workers were being evacuated from platforms in the Gulf of Mexico on Sunday, but no oil production was shut in.

The Louisiana Offshore Oil Port, or LOOP, which takes in an average of 1 million barrels of foreign crude from cargo ships daily, stopped offloading tankers shortly after noon CST Sunday (1800 GMT) due to deteriorating sea conditions, according to a spokeswoman.

The LOOP is the only U.S. port capable of handling the largest crude oil tankers.

Hurricane Ida was packing 100 mile-per-hour (161 kph) winds on Sunday, according to the U.S. National Hurricane Center, which rated it a Category 2 storm on the five-step Saffir-Simpson scale.

Ida is forecast to strike the U.S. Gulf Coast between Louisiana and Florida sometime Tuesday morning, the Hurricane Center said.

ConocoPhillips (COP.N) and Exxon Mobil Corp (XOM.N) said operations in the Gulf of Mexico were continuing as normal on Sunday while the company monitors the storm's progress.

The LOOP continues to supply U.S. Gulf Coast refineries from tens of millions of barrels of oil stored onshore despite the halt in tanker offloading, said LOOP spokeswoman Barb Hestermann.

The LOOP also continues receiving via pipeline 500,000 barrels per day (bpd) in oil from the Mars and Thunder Horse production platforms in the Gulf, Hestermann said.

"We may not be offloading tankers Monday and Tuesday as well," she said.

The Gulf of Mexico accounts for 25 percent of U.S. oil production and about 15 percent of national natural gas output. according to the U.S. government. (Reporting by Erwin Seba and Bruce Nichols; Editing by Jan Paschal)