Theresa May has hailed the progress being made in Brexit negotiations as EU leaders prepare to approve the terms of a transition phase after the UK’s exit.

The 27 leaders are set to endorse a 21-month transition period after March 2019, when the UK officially leaves.

The UK prime minister says she wants a “new dynamic” as talks move on to the economic and security relationship.

She also welcomed the US exemption for EU firms from tariffs on steel imports but is pushing for further action.

The Trump administration has decided to temporarily exclude the EU, as well as a number of other countries, from paying tariffs of 25% on steel imports due to come into effect on Friday.

Mrs May said this was welcome but what was needed was a permanent exemption, given the “huge importance” of the industry to the British economy and government.

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“I want to ensure that steel workers and their jobs are properly safeguard,” she said.

Mrs May has remained in Brussels for the second day of the EU Council summit to discuss steel and other trade issues although she will not be present when her colleagues meet to rubber stamp the transition period and consider approving guidelines for the second phase of negotiations.

Ahead of their meeting, she told reporters: “We’ve made good progress on the withdrawal agreement.

“But also I’m looking for a new dynamic in the next stage of the negotiations so that we can ensure that we do develop, that we work together to develop, a strong future economic and security partnership which I believe is in the interest of the UK and the European Union.”

From Russia to Brexit

By the BBC’s Europe editor Katya Adler

After a night of heated dinner debate over Russia, EU leaders turn their palates and attention this morning to a breakfast – though as this summit timetable keeps shifting, possibly brunch – discussion about Brexit.

The two issues are closely linked.

Theresa May came to Brussels looking for a robust response to the Salisbury attack. This was important for her not just in security terms. It was also her first test after a year of often bad-tempered Brexit negotiations to see if she could still rally European support in times of need. She could.

• Read Katya’s full blog

At a dinner on Thursday night, Mrs May said the UK and EU should work on issues like Northern Ireland, trade and security with “energy and ambition”.

“We have the chance now to work together to explore workable solutions – in Northern Ireland, in our future security co-operation and in order to ensure the future prosperity of all our people.”

She added: “This is an opportunity. It is our duty to take it and to enter into it with energy and ambition.”

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The UK is set to leave the bloc on 29 March 2019, but earlier this week Brexit Secretary David Davis and EU chief negotiator Michel Barnier struck a deal that would allow for a transition period – which the UK government describes as an implementation period – until December 2020.

Under the terms of that joint legal text, the UK will be able to negotiate, sign and ratify its own trade deals, while EU citizens arriving in the UK will enjoy the same rights and guarantees as those who arrive before Brexit.

A solution to avoid a hard border on the island of Ireland has yet to be agreed, with the EU insisting on a “backstop” option of Northern Ireland effectively remaining in the customs union.

EU Council president Donald Tusk said on Thursday he was “absolutely sure” a solution would be found to prevent the return of physical checks on the border between Northern Ireland and the Republic of Ireland.

The Irish government has insisted the UK has provided a “cast-iron guarantee” that will ensure no physical infrastructure, checks or controls at the border after withdrawal.

On Thursday, the European Council agreed with the UK that it was “highly likely” Russia was behind the Salisbury attack, Mr Tusk saying there was “no other plausible explanation”.