Aso, whose comments have angered Beijing in the past, said over the weekend that a consular official who committed suicide in Shanghai was blackmailed by Chinese intelligence agents who set him up with a woman to obtain classified information.
"I was just offering it as an example" he said on Monday. "It did not have any meaning beyond that."
The aftermath of the May 2004 suicide has further enflamed tensions between the two nations.
China has objected to suggestions by Japanese politicians that the official, whose name has not been released, was driven to suicide by Chinese spies.
On Saturday, Aso said in a speech in Tokyo that the man killed himself after having an affair with the unidentified woman.
The Foreign Ministry said there was no sign that the official had leaked information.
Aso's description of the situation was detailed.
"They approached him, offering to arrange a sexy woman for him," Aso said on Saturday.
"They approached him, offering to arrange a sexy woman for him. Then he was blackmailed to give away secret codes for classified information. It is clear from a suicide note he left"
Japanese Foreign Minister
"Then he was blackmailed to give away secret codes for classified information. It is clear from a suicide note he left."
Aso said the diplomat chose to kill himself rather than betray his country.
The government has since ordered changes to codes securing classified information and communication systems at Japanese embassies and consulates around the world.
But on Monday, Aso told lawmakers the account was hypothetical.
"As I said then, it is possible to think at the very least that Chinese authorities on the ground were talking about extortion, intimidation, and similar matters, but anything beyond that I can't really say," he said.
"Given that this kind of concern comes up from time to time, I was trying to say that diplomatic staff should just be careful."
Aso said male diplomats approached by attractive women should "clear off a mirror" and ask if they were really good-looking enough to deserve such attention.
The incident prompted Japan last month to accuse China of violating the Vienna convention on diplomatic relations that guarantees the inviolability of diplomats.
In response, Beijing issued a harsh protest.
The Foreign Ministry has also urged embassy and consulate workers worldwide to be on their guard, and ordered all its staff in China to use extra caution against spy activities.
Relations between Tokyo and Beijing have been battered in recent months by a string of disputes.
The two sides have argued over visits to a Tokyo war shrine by Junichiro Koizumi, the Japanese prime minister, undersea gas deposits in the East China Sea and other issues.