Mr Støre said the letter had come in response to a short message he had sent to Mr Trump earlier in the day.
The White House has yet to confirm the meeting.
The incident occurred the week after some 20 Russian drones entered Polish airspace.
Poland has requested consultations under Article 4 of the NATO treaty relating to external threats, Prime Minister Donald Tusk said in Warsaw on Wednesday.
“Last night in Poland, we saw the most serious European airspace violation by Russia since the war began, and indications suggest it was intentional, not accidental,” Ms Kallas stated.
Messrs Putin and Zelensky have not met since December 2019.
Mr Trump appears to be frustrated with Mr Putin’s determination to continue the war in Ukraine despite overtures from the American leader seeking a ceasefire and peace deal.
International Atomic Energy Agency head Rafael Grossi, in an interview broadcast on Sunday, said Iran could resume enriching uranium within months.
In addition, South Korea is set to participate in future NATO defence projects, though specific initiatives were not detailed.
Before both sides confirmed that a ceasefire was in place early Tuesday, they exchanged fire.
