Two major broadcasters have refused to air an advertisement urging Americans to protest the building of a mosque and Islamic cultural center just blocks from the ruins of the World Trade Center.

NBC and CBS refused to broadcast the 60-second ad, which is sponsored by the National Republican Trust, a conservative organization that promotes "American values" and supports candidates running for office.

The ad, titled "Kill the Ground Zero Mosque," received more than 134,000 hits on YouTube as of 1:30 p.m. Thursday. It contains graphic footage of the Sept. 11 attacks, including a clip of one of the planes crashing into one of the Twin Towers and a man plunging to his death. It also captures images of Islamic militants.

The ad encourages Americans to join the fight to "kill the ground zero mosque."

"On Sept. 11, they declared war against us and to celebrate that murder of 3,000 Americans, they want to build a monstrous 13-story mosque at ground zero," the narrator says. "Where we weep, they rejoice. That mosque is a monument to their victory and an invitation for war. A mosque at ground zero must not stand."

NBC Universal advertising standards manager Jennifer Riley said the use of the word "they" is open for misinterpretation.

"An ad questioning the wisdom of building a mosque at ground zero would meet our issues of public controversy advertising criteria," she wrote in a letter. "However, this ad, which ambiguously defines 'they' as referenced in the spot, makes it unclear as to whether the reference is to terrorists or to the Islamic religious organization that is sponsoring the building of the mosque. Consequently, the ad is not acceptable under our guidelines for broadcast."

Although CBS did not issue an official statement, a representative told The Washington Times that the ad "did not meet broadcast standards."

The National American Trust could not be reached for comment as of late Thursday afternoon.

Plans to build the $100 million, 13-story Islamic center near the site of the Sept. 11 attacks has been a hot topic since May. Critics say it would be inappropriate and insensitive to families who lost loved ones during the attacks.

Building plans for the mosque have yet to be approved. A vote is expected in August.