Michael Powell wants to spend more time with his wife and two boys

His term was due to run till 2007 but, in a surprise move, he now expects to step down in March.

He is best known as an advocate of free-market competition and for cracking down on indecency after singer Janet Jackson's top popped open on TV.

Mr Powell didn't say what he would do next professionally.

Taking time out

However, in a statement he said: "I look forward to spending some time off with my wife and two boys, before taking up my next challenge."

"They have been wonderfully supportive and patient."

Howard Stern welcomed Michael Powell's imminent departure

Analysts said Mr Powell had made improvements in the wireless communications area, where it had become easier to trade radio spectrum.

However, he has not always seen eye to eye with other members of the FCC, the US body which regulates the communications industry.

There was disagreements, for example, over whether large US media groups should be allowed to get even larger.

Howard Stern, the controversial US "shock jock" DJ, welcomed Mr Powell's departure, according to Bloomberg TV, as he felt the indecency crackdown limited freedom of expression.

Mr Stern was dropped by six stations owned by media giant Clear Channel in 2004 after it had to pay the Federal Communications Commission $1.75m (£950,000), over breaches of indecency laws.

The FCC has a number of key issues to deal with, including how to regulate companies providing voice calls over the internet.

It must also reform the Universal Service Fund, a federal subsidy programme that is under financial pressure.