Making telephone calls in southwestern Pennsylvania is about to get more complicated.

The state Public Utility Commission says growing demand for telephone numbers means a new 878 area code will soon be assigned to customers within what is now the 724 area code.

PUC spokeswoman Denise McCracken says the first numbers with an 878 area code could be issued in about two months but maybe not for a year, depending on when the 724 numbers are exhausted.

The 724 area code covers some or all of 14 counties: Allegheny, Armstrong, Beaver, Butler, Clinton, Crawford, Fayette, Greene, Indiana, Lawrence, Mercer, Venango, Washington and Westmoreland.

No immediate changes are anticipated in the 412 area code, which primarily covers the city of Pittsburgh.