Verizon Wireless expects to report a decline of up to 6 percentage points in its fourth quarter gross profit margins on strong sales of the Apple Inc iPhone and other devices, according to a top executive for its parent company.

Shares in Verizon Communications fell 1.3 percent after Chief Financial Officer Fran Shammo said during a webcast of an investor conference on Wednesday that wireless profit margins fell to a range of 42 percent to 43 percent in the quarter from 47.8 percent in the third quarter.

For 2012, Shammo said the company plans cuts in wireless expenses similar to last year's. In 2011 costs were reduced by $1.8 billion.

But he noted that the company's pension contribution obligations would rise to $1.2 billion in 2012 from about $400 million in 2011. The additional pension funding will come from the company's traditional telephone business, Shammo said.

Verizon Wireless' costs rose in the fourth quarter because the venture with Vodafone Group Plc sold 4.2 million iPhones and 2.2 million other smartphones using Verizon's highest-speed wireless network.

High smartphone sales always pressure margins because operators manufacturers higher subsidies to offer advanced phones at attractive prices. In exchange, consumers must sign a two-year contract. Subsidies for the iPhone have historically been higher than for other smartphones.

But Shammo said the company was pleased with the strong smartphone sales as these customers spend more money with Verizon in the long run.

This gives us a great momentum going into 2012, the executive said.

He also noted that the strong fourth quarter sales brings Verizon Wireless extremely close to its target for 11 million iPhone sales in 2011. Shammo also the company ended the year with a backlog of 120,000 iPhone orders.

Verizon Wireless, the biggest U.S. mobile service, also sold 2.2 million smartphones that run on its high-speed wireless network, Verizon said on Wednesday.

Verizon Communications shares closed down 52 cents at $39.21 on New York Stock Exchange on Wednesday. In comparison shares in its biggest rival AT&T Inc closed up 5 cents at $30.43.

(Reporting By Sinead Carew; Editing by Richard Chang)