I regret that I am unable to accept your kind invitation.

很遗憾，我不能接受你的友好邀请。

《牛津词典》

I am unable to move from here.

我无法搬离这里。

youdao

So currently, I am unable to make any promises.

因此我现在不能给出任何承诺。

youdao

"I am unable to have printed business cards due to budget restraints, " Patrick T.

WSJ: Smitten by Smiths: Bob Ziegler

"I am unable to conclude that there was eye-gouging in the sense of a ripping or aggressive intrusion of the eye area, " added Hudson.

BBC: Burger denies being 'rugby thug'

There is much left to do and I am very sorry to have been put in a position where I am unable to continue this work.

BBC: Short's resignation statement