UPDATE 1-Marriott quarterly profit beats on lower tax rate

(Adds details on the quarter)

May 10 (Reuters) - Marriott International Inc reported a better-than-expected quarterly profit on Friday, as the world's biggest hotel chain benefited from a lower effective tax rate and higher room rates.

Expanding U.S. economy has driven demand for corporate travel, benefiting the owner of Ritz-Carlton and St. Regis luxury hotel brands.

However, an increase in existing tariffs on $200 billion worth of Chinese goods to 25% from 10% at 12:01 a.m. ET (0401 GMT) on Friday may threaten global economic growth in the quarters ahead, affecting travel demand, analysts have warned.

Marriott reaffirmed its full-year worldwide revenue per available room (revPAR) forecast between 1% and 3%. RevPAR, a key measure of hotel health, is calculated by multiplying a hotel's average daily room rate by its occupancy rate.

The company raised its full-year 2019 adjusted profit forecast in the range of $5.97 per share to $6.19 per share, from a previous forecast of $5.87 per share to $6.10 per share, partly due to a lower effective tax rate.

On an adjusted basis, the company earned $1.41 per share, beating the average analyst estimate of $1.34 per share, according to IBES data from Refinitiv.

Revenue rose marginally to $5.01 billion in the quarter. (Reporting by Ankit Ajmera in Bengaluru; Editing by Arun Koyyur and James Emmanuel)