A U.S. prosecutor investigating the leak of a CIA agent's name has presented a handwritten note from Vice President Dick Cheney referring to the agent before the leak took place.

Special prosecutor Patrick Fitzgerald filed the note in court papers in the case against Cheney's former chief of staff, I. Lewis Libby.

The filing says Cheney made the notes on an article written by the agent's husband, Joseph Wilson, about a trip to Niger to probe alleged uranium sales to Iraq.

It says Cheney asked if officials had approved the trip, or if Wilson's wife, Valerie Plame, had sent him on a "junket."

The court filing says the note shows that Cheney and Libby were "acutely focused" on Wilson's claims in the article and on rebutting his criticism of the White House.

In the article, Wilson says he found no evidence of uranium sales and charged the White House had manipulated intelligence to justify the war in Iraq.

He has said administration officials leaked his wife's name to reporters in an effort to discredit him, after the article was published.

Some information for this report was provided by AFP, AP and Reuters.