Britain's House of Lords will Monday begin detailed scrutiny of the bill empowering Prime Minister Theresa May to kickstart Brexit, with the fate of EU nationals living in Britain likely to be on the agenda.
The lower House of Commons overwhelmingly approved the draft legislation earlier this month, and the unelected upper house has already held two days of debate before now examining the short bill line-by-line.
Peers will be able to propose amendments that could potentially delay May's plans to trigger Article 50 of the EU's Lisbon Treaty -- a formal notification of Britain’s intention to leave the bloc -- by the end of March.
This would fire the starting gun on a maximum of two-years negotiations with the EU to work out the divorce deal and terms of a future relationship, with Britain automatically leaving the bloc if no agreement is reached by then.
Peers are set to discuss on Monday and Wednesday proposals including measures to guarantee the rights of EU nationals in Britain, and defining the parameters of a parliamentary  vote on the final Brexit deal. 
The so-called "committee stage" is the first opportunity for peers to make amendments, which would then get debated and voted on before being passed back to the House of Commons for approval.
If the Lords approves the bill without amendments it will be sent,  after its final reading on March 7, directly to Queen Elizabeth II to sign into law.
However, if there are amendments, the bill could bounce between the two houses as they try to agree on its final wording, potentially derailing May's timetable.
- No 'blank cheque' -
The government presented the short bill to parliament in January after losing a high-profile court battle in which judges ruled May must consult the legislature before beginning the EU divorce proceedings.
The unamended legislation sailed through the Commons this month by 494 votes to 122.
But the government could face greater challenges in the Lords, where only 252 of the more than 800 members are from May's ruling Conservative party.
Dick Newby, leader of the Liberal Democrats in the upper house, said there was strong support among peers for protecting the rights of EU citizens.
There is "an overwhelming desire to do the right thing and ensure that all EU nationals have the right to remain," he was quoted as saying by the Guardian on Sunday.
Writing in the Mail on Sunday, Conservative peer Michael Heseltine, a former deputy prime minister, vowed to support opposition moves to secure a parliamentary vote on the Brexit deal within the bill.
- 'British people want Brexit' -
May has urged the Lords to neither amend the bill nor delay it.
"There will be debate and scrutiny in the House of Lords, but I don't want to see anybody holding up what the British people want... which is for us to deliver Brexit, to leave the European Union," she said.
Interior Minister Amber Rudd on Sunday said she thought there was no chance of May accepting any amendments.
"No I don't think there is any possibility and I don't think there should be," she told ITV television, adding there would be "opportunities to debate and discuss" during the two years of Brexit talks.
But during the initial two-day Lords debate last Monday, Labour peer Angela Smith said peers should not "provide the government with a blank cheque" and that they would not be intimidated by MPs who have suggested the upper house could be abolished if it delays the bill.
Conservative MP Dominic Raab had earlier warned that "peers would be wise to consider this clear democratic mandate, and their own futures, when debating the Article 50 bill."

Source: AFP