I am not a native English speaker. So my explanation might not be clear. Still I will try to explain. Please forgive my bad English.
When I was writing an email, I want to convey this meaning:
"We can plan to complete this by Monday or if in case it is not completed on Monday(which is not desirable, but can be tolerated in a worst case scenario. But it is a must that it should be completed on Tuesday), then the maximum time we can wait for the completion of the task is Tuesday".
How I can write this concisely and in a less complicated way. Something such as:
We can plan to complete this by Monday or ----- by Tuesday.
Is there a single word that I can use to fill in the blanks, that will convey the meaning that the task must not be extended after Tuesday? I thought the word lately will fit there, but it has somewhat opposite meaning.