He has made the statement in a comment to CNBC in Chisinau, where the second meeting of the European Political Community is taking place, Sky news reports.
"I agree with the NATO secretary general that Ukraine's rightful place is in NATO," Sunak said.
The British Prime Minister noted that the allied countries are sending a strong message to Russian leader Vladimir Putin, affirming their commitment to ensuring the long-term security of Ukraine.
"We want to make sure we put in place security arrangements for Ukraine for the long term, so we send a very strong signal to Vladimir Putin that we are not going anywhere, we are here to stay and we will continue backing Ukraine - not just now, but for years into the future," Sunak said.
President Zelenskyy took part in the summit of the European Political Community (EaPc) hosted by Moldova on June 1.
On April 20, during a visit to Ukraine, NATO Secretary General Stoltenberg said that Ukraine has a rightful place in the Euro-Atlantic family and in NATO.