Some 35 US evangelical organisations with membership of about 50 million people have written to President George W. Bush saying military intervention in Darfur should be considered.
"The administration needs to understand this constituency is serious about Darfur," Mr Richard Cizik of the National Association of Evangelicals said.
Christian conservatives - a key support base for President Bush - have focused on Sudan for years because of a separate conflict between the Islamic government and Christians in the south.
US State Department spokesman Mr Richard Boucher, who has accused Sudan forces of helping the militia, said, "The provision of additional security forces may be a necessary step to provide security for the people of the area, but it's only one of many steps they should be taking."
UN Secretary-General Mr Kofi Annan has warned the Sudanese government to comply with a UN resolution threatening sanctions and says he believes Khartoum was getting the message "loud and clear".
The Security Council adopted a resolution last Friday giving Sudan 30 days to disarm and prosecute marauding militia in its western region of Darfur or it would consider unspecified sanctions against Khartoum.
"I think the resolution is very clear, that if they do not perform, there will be consequences, and I think the government of Sudan has got the message loud and clear. You can tell by their reaction," Mr Annan told reporters on Tuesday.
"The council is insisting that they just protect their own population," Mr Annan said. "They must show demonstrably that they are determined, they are serious, and they are protecting the people, and this has to be seen by the people and felt by the people, not by public declarations."
Mr Annan a month ago signed an agreement in Khartoum, in which the government pledged to provide security to uprooted African villagers, chased from their homes by Arab militia, called Janjaweed, with the aid of the Sudanese military.
The Janjaweed are accused of murder and rape, driving 1 million people into barren camps and leaving 2 million people in need of shelter, food and medicine.
The United Nations estimates 30,000 people have died since fighting began early last year, and US officials say as many as 50,000 more may have died from hunger and disease.
In Khartoum, African rebels were accused by Sudanese officials of masquerading as Janjaweed before killing 38 people from the Rizeiqat Arab tribe in southern Darfur.
The rebels are part of a revolt that broke out in western Sudan in early 2003 among African villagers protesting their treatment by Khartoum. The government turned to the largely nomadic Janjaweed to suppress the rebels.