US authorities have eyed North Korea as the origin of the widespread cyber attack that overwhelmed government Web sites in the United States and South Korea, although they warned it would be difficult to definitively identify the attackers quickly.

The powerful attack that targeted dozens of government and private sites underscored how unevenly prepared the US government is to block such multi-pronged assaults.

While Treasury Department and Federal Trade Commission Web sites were shut down by the software attack, which lasted for days over the holiday weekend, others such as the Pentagon and the White House were able to fend it off with little disruption.

The North Korea link, described by three officials, more firmly connected the US attacks to another wave of cyber assaults that hit government agencies Tuesday in South Korea. The officials said that while Internet addresses have been traced to North Korea, that does not necessarily mean the attack involved the Pyongyang government.

The officials spoke on condition of anonymity because they were not authorized to speak publicly on the matter.

South Korea intelligence officials have identified North Korea as a suspect in those attacks and said that the sophistication of the assault suggested it was carried out at a higher level that just rogue or individual hackers.

US officials would not go that far and declined to discuss publicly who may have instigated the intrusion or how it was done.

In an Associated Press interview, Philip Reitinger, deputy under secretary at the Homeland Security Department, said the far-reaching attacks demonstrate the importance of cybersecurity as a critical national security issue.

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