(Adds details on other countries, Android market share numbers, background)
Dec 5 (Reuters) - The unavailability of the iPhone X during the three months ended October pulled down the market share for Apple's iPhones in some key regions, while phones running on Google's Android recorded higher sales, data from a research firm showed on Tuesday.
The market share for Apple Inc's iPhones, as measured by sales of its iOS mobile operating system, declined to 32.9 percent in the United States, from 40.6 percent a year ago, Kantar Worldpanel ComTech's data showed.
In an analysis of smartphone operating system sales for the quarter ended October, Kantar also said iOS market share slipped in Japan and key European markets, while Android clocked gains in most markets.
The iPhone X, the 10th anniversary edition of the smartphone, was launched in early November, more than a month after the iPhone 8's launch on Sept. 22.
"It was somewhat inevitable that Apple would see volume share fall once we had a full comparative month of sales taking into account the non-flagship iPhone 8 versus the flagship iPhone 7 from 2016," said Dominic Sunnebo, global business unit director at Kantar.
Android, Google's open-source platform, is the leader in mobile operating systems and is adopted by a majority of smartphone makers.
In the October-quarter, Android's market share rose to 66.2 percent in the United States from 58 percent a year ago. Android also gained in other countries including Japan, Britain and Germany. (bit.ly/2jgOZe1)
Urban China was a bright spot for Apple as iOS market share edged up 0.5 percentage points to 17.4 percent. Android's share fell slightly to 82.3 percent. (Reporting by Munsif Vengattil in Bengaluru; editing by Sai Sachin Ravikumar)