The UK is leading the way with its Rwanda deportation scheme as other European countries look at "similar solutions" to tackle illegal immigration, the prime minister has said.
Mr Sunak said they discussed how they can "work together" to tackle the "shared challenge" of illegal immigration in Europe.
The Conservative government wants to send tens of thousands of migrants more than 6,000 miles away from the UK to Rwanda as part of a £120m deal agreed with the east African country in 2022.
Critics have claimed the policy breaks international human rights laws, and no one has been sent to the country yet after ongoing legal challenges in the courts.
Mr Sunak has said he will do "whatever is necessary" to get the removal flights going after a Court of Appeal ruling in June said the scheme is unlawful.
The government later confirmed it would be submitting an appeal to the Supreme Court to try and reverse the ruling.
Sunak says UK has taken 'radical action'
Speaking about the Rwanda policy to reporters in Delhi, Mr Sunak said on Saturday: "I've always said that this is a global issue, this issue of illegal migration. It is only growing in importance and will require global coordination to resolve.
"I have said Britain would be tough but fair, and where Britain leads others will follow. We have been willing to take bold and radical action to tackle this problem.
"I said that other countries would look at similar solutions, and you can start to see that they are with the news from Austria this week, and more broadly across Europe.
"You can just see this issue growing and growing in salience, and I think that we have been out in front leading the conversation on this and the need to look at this differently and look at radical solutions."
Austria and Denmark consider Rwanda plan
Mr Sunak's comments come after Austrian Chancellor Karl Nehammer raised the possibility of deporting illegal immigrants to Rwanda, where their cases for asylum cases would be processed.
Gerhard Karner, Austria's interior minister, has called for the EU to introduce "asylum procedures in safe third countries" and referred to a model "Denmark and Great Britain are also following".
Denmark had been in negotiations with Rwanda over the possible transfer of asylum seekers.
However, the plans were put on hold earlier this year as Denmark wants to work for an EU-wide solution.
It comes after Italy's prime minister, who heads up a right-wing government, defended the UK government's Rwanda policy in April.
She said it was wrong to refer to it as "deportation" and any suggestion Rwanda does not "respect rights" would be a "racist way of interpreting things".
However, there are no reports to suggest Italy has been considering sending illegal immigrants to the east African nation.
Sunak wants UK and Italy to 'do more together'
Speaking about his meeting with Ms Meloni at the G20 summit, Mr Sunak said: "Obviously (illegal immigration) is something that her and I have talked about a lot and we talked again about how we can work closer together, which we're already doing.
"But again, what are the opportunities for us to do more together to tackle this shared challenge?"... She and I have a view together, both of us, that this is an important topic that needs us to work together.
"So that won't be the last of these conversations that I have."
Mr Sunak is visiting New Delhi for the first as prime minister while he is at the G20 summit.
He has said he is confident a trade deal will be struck between the UK and India after meeting with the country's prime minister Narendra Modi.
The annual G20 summit brings together leaders from 20 of the world's largest economies to discuss pressing global issues.