WASHINGTON — The White House acknowledged Monday that an attempt was made to infiltrate its computer system, but it said it thwarted the effort

A White House official said the attack targeted an unclassified network. He said the attack was identified and the system was isolated. There was no indication that any data were removed.

The official, who was not authorized to speak on the record about the attack, said there was no attempted breach of classified systems. The official described such ‘‘spear-phishing’’ attacks as ‘‘not infrequent.’’

Last year, Google Inc. blamed computer hackers in China for a phishing effort against Gmail accounts of several hundred people, including senior US government officials and military personnel. Last November, senior US intelligence officials for the first time publicly accused China of systematically stealing American high-tech data for its own national economic gain.

The White House would not say whether the recent attack was linked to China.

Defense Secretary Leon Panetta, during a visit to China last month, raised the subject of China-based cyberattacks against American companies and the government.

News of the most recent attack came as the Obama administration is preparing an executive order with new rules to protect US computer systems.

After Congress failed this summer to pass a cybersecurity bill, the White House said it would use executive branch authority to improve the nation’s computer security.