She said the sanctions would be aimed at the sale or procurement of arms and related goods as well as the procurement of luxury items.
The US will freeze assets as well as prevent some businesses and individuals from travelling abroad, and collaborate with banks to stop illegal financial transactions, Clinton said.
Clinton arrived in Seoul, the South Korean capital, on Wednesday, with tensions between the North and South running high following the recent sinking of a South Korean warship, which left 46 sailors dead.
"From the beginning of the [Barack] Obama administration, we have made clear that
there is a path open to the DPRK to achieve the security and international respect it seeks,'' she said, referring to North Korea by its official name, the Democratic People's Republic of Korea.
"North Korea can cease its provocative behaviour, halt its threats and belligerence towards its neighbours, take irreversible steps to fulfill its denuclearisation commitments and comply with international law,'' Clinton said.
Andrei Lankov, a North Korea expert based in Seoul, told Al Jazeera that new sanctions were unlikely to have much impact or significance in the North.
"They [the sanctions] were expected, especially when the UN Security Council chose to have a very cautious approach to North Korea and did not introduce new sanctions, it was only logical that America would do something," he said.
"They [the sanctions] don't look impressive - very few countries sell arms to North Korea and those who do are not likely to be influenced by any decision made by the US.
"The idea to freeze assets of North Korea's elite has been tried before. Their lifestyle could become difficult but I do not expect it to change their policies."
Earlier, during a visit to the Demilitarised Zone that divides the two Koreas, Clinton was accompanied by Robert Gates, the US defence secretary, who remarked on the contrast between the prosperous South and the impoverished, communist North.
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"In the 20 years since I last climbed that observation tower and looked out across the DMZ, it's stunning how little has changed up there and yet how much South Korea continues to grow and prosper," he said.
"The North, by contrast, stagnates in isolation and deprivation."
Clinton and Gates were visiting South Korea to underscore their support for Seoul following the sinking of the Cheonan in March.
The North has denied it is reponsible for the incident and a United Nations Security Council statement condemning the sinking did not name North Korea as the culprit, apparently after Chinese pressure.
US officials have suggested that the apparent torpedo attack on the Cheonan could herald further attacks on the South, but some analysts have said this is unlikely given the situation in the North.
Don Kirk, the Koreas correspondent for the Christian Science Monitor newspaper, told Al Jazeera that the claim that North Korea's behaviour may turn even more aggressive is overstated.
"I don't think North Korea is in a position to stage more attacks. The country is facing severe economic problems, and also, China is trying to hold North Korea in check," he said.
"I think that after these military exercises are held, the whole direction will be towards six-party talks on its nuclear programme."
The US has sent the 97,000-tonne aircraft carrier USS George Washington to take part in drill set to begin on Sunday in the Sea of Japan.
The exercises will involve about 20 ships and 200 fixed-wing aircraft, according to military officials.
North Korea has denounced the exercises as "very dangerous sabre-rattling".