"The message I plan to give ...is that the cause of these problems we have is in Baghdad and Saddam Hussein who refuses to abandon his pursuit of weapons of mass destruction," he said.
At a joint news conference with Russian Foreign Minister Igor Ivanov, Mr Powell said that Iraqi leader Saddam Hussein was a danger not only to the US but also the whole Middle East.
Mr Powell was in Cairo at the start of a six-nation tour of the Middle East, his first foreign trip since taking office.
He said he recognised that some in Egypt were unhappy about the air raids on Iraq, but maintained they were justified.
He said the purpose behind the sanctions policy was as important as when it was imposed over 10 years ago.
The Egyptian Foreign Minister Amr Moussa said every chance had to be given to talks about the sanctions next week between Iraq and the United Nations.
'Saddam is the problem'
Mr Powell brought Washington's case for the legitimacy of air strikes directly to Arabs.
"The message I plan to give ...is that the cause of these problems we have is in Baghdad and Saddam Hussein who refuses to abandon his pursuit of weapons of mass destruction," he said.
The trip is being seen partly as an attempt by Mr Powell to improve relations with Middle Eastern countries following the bombing.
Correspondents say the challenge for the United States is to stop Iraq obtaining military technologies while ensuring that Baghdad cannot blame sanctions for the hardships of ordinary Iraqis.
The sanctions, first imposed in 1990 after Iraq invaded Kuwait, were initially supported by most Arab countries.
But the measures have been crumbling, with more and more oil being exported from Iraq outside the UN system.
Crowded trip
Mr Powell is now in Tel Aviv, where he met outgoing Prime Minister Ehud Barak on Saturday evening and Prime Minister-elect Ariel Sharon the following morning.
The other stops on the crowded four-day schedule are Jerusalem, Gaza, Amman, Kuwait, Damascus and Riyadh, with a day in Brussels on his way home on Tuesday.
In Israel he is due to listen to the proposals of the parties involved in the Arab-Israeli conflict, but with Mr Sharon still trying to form a government, US officials do not expect any bold initiatives.