Theresa May has vowed to make it as easy as possible for EU citizens to remain in the UK after Brexit ahead of a key summit of European leaders, BBC reported.
In a Facebook post, the prime minister insisted the application process for settled status would be "streamlined" and the cost "as low as possible".
Campaigners welcomed her message but said it seemed more aimed at persuading the EU to progress Brexit talks.
The PM will address EU leaders at a summit in Brussels later.
The leaders of the other 27 member states will then consider the overall progress in the talks so far.
At a meeting on Friday, at which the UK will not be present, they are expected to conclude officially that "insufficient progress" has been made on the first topics for discussion to move onto the second phase of trade discussions.
A group of pro-Brexit politicians is urging her to make clear she will walk away from talks unless the EU changes its stance.
European Council President Donald Tusk said there would be no "breakthrough" at the two-day summit, but progress could be achieved by the next scheduled meeting of EU leaders in December.
As well as citizens' rights, agreement has yet to be reached on the UK's financial obligations to the EU and the border in Northern Ireland.
Before leaving for Brussels, Mrs May used her Facebook post to offer further assurances to the three million or so nationals of other EU countries living in the UK and uncertain about their future after Brexit.
In her message, she said those who already had permanent residence would be able to "swap this" for settled status in as hassle-free a way as possible