The letter should include specific details like your relationship with the visitor, the purpose of their visit, duration of stay, and financial arrangements. Comprehensive guide to writing an invitation letter for your US visa application, with free samples and tips.While the US resident can write an invitation letter, the visa officer will never use it to evaluate the applicant's eligibility for a visa. Temporary religious worker (R-1) visas are for persons who want to work temporarily in the United States in religious capacities. To write a letter for a conference visa invitation, use a professional tone, provide accurate information, and keep it concise and clear. Greetings in the name of our Lord and Savior Jesus Christ! The template is designed in both A4 and US letter sizes, accommodating international and domestic visa requirements. The invitation letter must be in the English language, so that US officials can read it.