After sailing through the House of Commons earlier the month by 494 votes to 122, the UK's proposed Brexit legislation faced a less smooth road ahead on Monday as the House of Lords began two days of debating the bill.
With Prime Minister Theresa May's Conservative Party not holding a majority in the unelected chamber, peers could potentially seek to push through amendments to the law.
Included in the 11 pages of proposed changes are measures to guarantee the rights of EU nationals already in Britain to stay, and a redefinition of how parliament votes on a final Brexit deal.
Although the peers will not block Brexit, any amendments to the bill could see May's government miss its scheduled deadline of triggering Article 50 of the Lisbon Treaty by the end of March.
Urging the Lords to follow the lead of the Commons by neither amending nor delaying the bill, May said she didn't "want to see anybody holding up what the British people want ... which is for us to deliver Brexit, to leave the European Union."
The legislation gives May the right to trigger Article 50, effectively beginning up to two years of formal divorce negotiations with Brussels, which were prompted by last June's EU referendum when 52 percent of voters favored leaving the 28-member bloc.
The Conservative government presented the short bill after losing a high-profile court battle in which judges ruled that May must have parliament's consent before beginning the UK's departure from the EU. Taking the bill to the House of Lords is the final step in that process.
Long weeks ahead
In an unusual but not unprecedented move for a prime minister, May made her presence felt on Monday as she also attended the debate at the House of Lords, sitting at the steps to the monarch's throne.
Following the "Second Reading" of the bill on Monday and Tuesday, the legislation will then enter the "Committee stage," scheduled for February 27 and March 1. During this stage any amendments will by discussed and may be voted on.
A third reading is then due to take place on March 7 during which the final wording of the legislation will be debated, before the bill is returned to the Commons with any amendments, most likely by the week commencing March 13.
Brexit Minister David Davis, in Tallinn in Estonia on Monday, said that May's government remained on track to trigger Article 50 by March 31. "I am confident we can meet that date," Davis said.
ksb/msh (AP, AFP, dpa)