兼(か)ねるCannot, Be unable to, Hard to, Hesitant to

兼(か)ねる, a る-Verb meaning 'to spread across' (usually 2 different activities or thought processes), often follows the ます-stem of other verbs in order to highlight that '(A) is not possible'. However, 兼(か)ねる often indicates that the speaker would actually like to do (A), but cannot due to some external circumstances such as difficulty, already being busy, being hesitant, etc.

This particular grammar pattern will most frequently be seen in its non-kanji form, although both are possible.

兼(か)ねる is somewhat formal, and may be used in cases where a phrase like できない would be considered too strong, so the speaker wants to lightly imply that (A) cannot be done.

Fun-fact

As 兼(か)ねる means 'to spread across', this expression can be thought of as similar to 'to be a stretch' in English. It just indicates that doing the action of (A) would be a stretch of the speaker's ability or capacity.