Yoko Ono has booked a series of ads in major US newspapers urging the country not to go to war with Iraq.
Ono has been a vocal opponent of the war
Ono, 70, has booked full-page adverts that read "Imagine Peace... Spring 2003", referencing the song her late husband John Lennon wrote.
The famous song has often been used as an anthem by peace activists.
The most recent of the adverts was in the San Francisco Chronicle on Wednesday.
The newspaper said Ono had spent $42,000 (£26,750) on the advertisement.
Other ads have run in the Los Angeles Times, the L.A. Weekly, and the Village Voice. Another is due to run in the Washington Post on the weekend.
Lennon's last song has been remixed into a dance hit by Ono
Ono also wrote a column for the Chronicle, saying she was angered by US broadcasting Clear Channel to ban the song Imagine from its playlists after the 11 September terrorist attacks.
She said they had "censored" the song by adding it to a list of tracks deemed unsuitable for broadcast after the attacks.
She said she had not involved any other artists in the campaign.
"I just did it myself," she wrote. "That way, there's no red tape, no waiting period for approval of other people or organizations."
Ono has been a vocal opponent of war for decades.
Recently, she played in New York and unveiled a dance music version of the song she released after Lennon's death.
The couple were working on the track - Walking on Thin Ice - the night Lennon was gunned down in New York in 1980.
She teamed up with British pop band Pet Shop Boys for the "electroclash" remake of the track.
She played it the night before her 70th birthday.