在外交活动中，建立正式的外交关系往往需要通过交换建交函的形式来实现。以下是一份简短的英文建交函范文：
[Date]
The Embassy of [Country A]
To: The Embassy of [Country B]
Subject: Establishment of Diplomatic Relations
Dear Sir/Madam,
We are pleased to inform you that the Government of [Country A] is eager to establish formal diplomatic relations with your great nation. We believe that this step will significantly enhance the mutual understanding and cooperation between our two countries.
Please find enclosed the draft of a bilateral agreement outlining the terms and conditions for the establishment of diplomatic ties. We look forward to your favorable response and are hopeful that this will mark a new chapter in our bilateral relations.
Sincerely,
[Name]
[Title]
Ambassador of [Country A]
以上范文简洁明了，适用于两国初次建立外交关系时的正式函件。