Donald Sachtleben, 55, is to be sentenced to 12 years in prison.
The May 2012 disclosures jeopardised an international intelligence operation and put lives at risk, officials said.
Investigators identified him after seizing phone records of the Associated Press, which published an article on the Yemen-based al-Qaeda plot.
"This unauthorized and unjustifiable disclosure severely jeopardized national security and put lives at risk," Deputy Attorney General James Cole said in a statement.
"To keep the country safe, the department must enforce the law against such critical and dangerous leaks, while respecting the important role of the press."
In May 2012, the Associated Press published an article describing a successful effort to disrupt a plot by Yemen-based al-Qaeda militants to bomb a US-bound airliner.
In court documents, Sachtleben of Indiana admitted giving a reporter information on a plot matching that description.
US Attorney General Eric Holder called the national security disclosure among the most serious he had ever seen.
"It put the American people at risk, and that is not hyperbole," he told reporters in May.
The Associated Press declined to comment on its relationship with Sachtleben, but said he had pleaded guilty "to revealing secret information for an Associated Press story".
Sachtleben worked for the FBI as a bomb technician from 1983-2008 and held top secret security clearance.
Stored secrets
In 2008, he was rehired as a contractor, maintaining his security clearance and continuing to have access to classified defence information, according to court documents.
On 2 May 2012, he disclosed secret information to a reporter, according to a court document he signed.
Nine days later he was arrested on separate charges of trading images of child pornography online, having been identified during an investigation into another man accused of possession of child pornography.
An FBI search of Sachtleben's computer, seized in the child pornography investigation, revealed improperly stored secret documents, according to court records.
On Monday, Sachtleben pleaded guilty to unauthorised disclosure of national defence information, unauthorised possession and retention of national defence information, and two charges of distributing and possessing child pornography.
The plea agreement calls for him to be sentenced to a total of 140 months in prison - 43 for the national security offenses and 97 for the child pornography charges.
参考译文：
综合外国媒体报道，美国司法部9月23日宣布，一名曾在美国联邦调查局（FBI）工作25年的排爆专家已向法庭认罪，承认向美联社泄露机密信息，如果法官接受其认罪协议的话，他将入狱12年。
2012年5月，美联社刊发了一篇报道，讲述美国情报和安全人员查获关联“基地”组织也门分支的新型炸弹、成功挫败一起恐怖分子针对飞往美国民航航班的袭击阴谋。然而奇怪的是，美国当局并未向媒体通报上述案件。
此后，有关部门进行了一场全面联邦调查、以查明事件原委。调查人员获取了20条美联社记者和编辑使用的电话线路的通讯记录，发现联邦调查局前雇员唐纳德·扎赫特勒本与美联社的一名记者过往甚密、十分可疑。
扎赫特勒本今年55岁，居住在印第安纳州卡梅尔镇。1983年至2008年，扎赫特勒本在联邦调查局工作，作为一名排爆专家，他拥有接触高级机密的权限。2008年，扎赫特勒本被雇为政府承包商，其工作权限被保留，他仍然可以获取机密国防信息。
根据法庭文件，调查人员从扎赫特勒本的“电子设备”中调取了电子邮件和短信，确认他早在2009年秋天就成为美联社一名“A记者”的线人。2012年4月30日至5月2日，扎赫特勒本与“A记者”多次联系，他就是在此期间向“A记者”透露了有关挫败恐怖分子袭击阴谋的机密信息，称联邦调查局“当时在进行一个持续中的、秘密的、敏感的炸弹分析”。
2012年5月11日，扎赫特勒本被控在网上交易儿童色情图片而被捕，他的电脑也被查封。联邦调查局搜查其电脑时，在其中发现了许多非法存储的机密文件。
“为保证国家安全，司法部必须确保如此严重、危险的泄露信息行为受到法律制裁，与此同时，也会依法保护新闻自由。”美国司法部副总检察长詹姆斯·科尔称，扎赫特勒本泄露机密信息“严重损害了美国国家安全、将民众的生命安全置于危险之中”。
华盛顿首席联邦检察官罗纳德·梅琴指出，在美军击毙本·拉登一周年之际披露美国当局发现恐怖分子使用新型炸弹意图袭击赴美民航客机，“这对敏感的情报行动构成了威胁”。“针对扎赫特勒本的起诉，反映出我们下定决心要把那些违背工作职责、无法保护国家机密不被泄露的人绳之以法的决心，同时也对其他人敲响了警钟，”梅琴说。
23日在法庭上，针对检方提出的泄露国防机密信息、非法存储国防机密信息、以及两项散布和持有儿童色情图片的指控，扎赫特勒本均承认有罪。根据认罪协议，数罪并罚，他将面临共计140个月的监禁，其中泄密罪和传播儿童色情照片罪分别需入狱43个月和97个月。
目前，美联社拒绝就扎赫特勒本案以及其与扎特特勒本的关系作出回应。
