职场英文拒绝额外加班要求，怎么说礼貌得体？

不要直接说"I can't"，可以用先肯定再说明情况的表达："I appreciate you trusting me with this extra task, but my current project deadline is this Friday and I won't be able to deliver quality work on this right now. Could we revisit this next week?" 翻译过来是："非常感谢您把这项额外工作交给我，不过我当前的项目这周五就要截止了，现在没法保证把这项工作做好，我们能不能下周再谈这件事？"既明确拒绝，又给对方留了台阶，说明自己是对工作质量负责，不是偷懒。