regrettably

Regrettably, the concert has been cancelled due to the lead singer's sudden illness.

(Chinese) 遗憾的是，由于主唱突然生病，音乐会已经取消了。

We would love to help you, but regrettably, we do not have any more funds available for this project.

(Chinese) 我们很想帮助你，但遗憾的是，我们没有更多的资金可用于这个项目。