NEW YORK — The San Antonio-based Christians United for Israel launched a letter-writing campaign on Monday demanding that Twitter ban Hamas from using its microblogging platform.

“The fact that a terrorist organization like Hamas, with so much Israeli and American blood on its hands, can use a service like Twitter is outrageous,” the group wrote in an “action alert” announcing the campaign.

In the letter CUFI is providing to supporters, the organization notes that “the United States government has designated Hamas as a Foreign Terrorist Organization. Under 18 U.S.C. 2339A, it is illegal for any US Company to provide ‘material support’ to a terrorist organization. This prohibited material support specifically includes ‘services’ and ‘communications equipment.’”

By allowing Hamas to have a Twitter account, the company is “providing it with an important ‘service’ and extremely effective ‘communications equipment’ which are central to its primary mission of terrorizing the Israeli people and using civilian deaths to score political points.”

Hamas-affiliated Twitter accounts, especially that of the Alqassam Brigades, have glorified rocket attacks on Israeli civilians and promulgated pictures of dead children alleged to have been killed by Israeli strikes – many of them discovered to have been copied from Syrian opposition website that claimed the children were victims of the violence in Syria over the past two years.

Allowing Hamas to use its platform for such activities, CUFI believes, amounts to “material support” to the terror group.

“The kind of behavior Twitter is engaged in is exactly the kind of behavior Congress wanted to prevent” by passing a law prohibiting such support, said CUFI executive director David Brog.

Twitter’s actions also violate the Supreme Court’s interpretation of the law, the group says.

“In its February 2010 opinion in Holder v. Humanitarian Law Project, the United States Supreme Court stressed that support for terrorists need not be directly linked to the commission of violent attacks to violate the material support statute,” the CUFI letter notes.

Over 12,000 supporters have sent the letter to Twitter in the first four hours of the campaign Monday afternoon.

Copies of each email were also sent to the San Francisco US Attorney’s office, in an effort CUFI hopes will lead federal authorities to examine the legality of allowing Hamas to use a US-based online social network.

The group has also launched a Twitter hashtag (or user-generated topic) called #BanHamas, and has called on supporters to use the hashtag on the site in an effort to get it to “trend,” or to appear on the list of most popular topics on Twitter’s homepage, making it possible for Twitter’s hundreds of millions of users to see the topic.

Requests for comment to Twitter and the US Attorney’s office in San Francisco were not immediately returned Monday evening.