The U.S. Olympic Committee wants to know if Philadelphia or Pittsburgh might be interested in hosting the 2024 Summer Olympics.

The committee said 35 letters were sent out Tuesday seeking to gauge interest. The nation's 25 largest cities got the letter, along with Pittsburgh and nine others.

Pittsburgh Mayor Luke Ravenstahl said there would be "extraordinary" challenges to submit a formal bid, but that he will seek community input about the offer. The letter suggests that hosting the event would require a budget of more than $3 billion.

The USOC said the letter is just an initial step in evaluating a potential bid, not a guarantee they will bid for the 2024 Games.

The U.S. hasn't hosted the Summer Olympics since Atlanta in 1996.