The Taoiseach Enda Kenny says Britain staying in the European Union is in "Ireland's interest, Britain's interest and Europe's interest".

He is in Brussels for a summit of EU leaders, over Britain's relationship with the bloc.

Mr Kenny says Ireland is "very supportive" of the UK staying within the EU - and hopes the talks can be concluded tomorrow.

Among the issues of contention are the details for changes to the payment of child benefit to children of non-British EU workers whose families reside in their home country.

If the deal goes through, child benefit for children living outside the UK will be paid at local rates.

In addition, the curtailment of in-work benefits for non-British workers in the UK is causing disquiet among countries that export low-skilled workers that benefit from such arrangements.

Four Eastern and Central European countries including Hungary and Poland are the most concerned about these changes.

The President of the European Council, Donald Tusk, says the talks are "make or break".

Speaking in Brussels before the talks, Mr Tusk had a simple message.

David Cameron has described the summit as a "once-in-a-generation" opportunity.

He told fellow EU leaders at the start of the Brussels meeting that the "festering" problem of the UK's ties to the union needed to be resolved.

The British prime minister appealed to them to help find a "credible" set of reforms that he can sell to Britons in a forthcoming in-out referendum.

Mr Cameron earlier said he was "battling for Britain" at the crunch summit and stressed he would "not take a deal that does not meet what we need".

Martin Schulz, the head of the European Parliament, earlier said he is "optimistic" leaders will strike a deal.

When asked if the summit could run into Saturday, he said: "I hope not, but if it's needed then we will continue".

German Chancellor Angela Merkel has said she wants to do everything to keep in Britain in the EU, while French President Francois Hollande said Britain can stay, but must abide by the EU's principles.

Organisers said the opening session overran and was extended to allow all the leaders the chance to comment on a draft text containing the reform proposals.

The topic of the summit is due to be the migration crisis overnight with reform discussions continuing on the sidelines.

Leaders will then switch back to the reform proposals at 10am Irish time tomorrow.

Mr Cameron is hoping a deal will be reached by the afternoon, after which he will return for a special meeting of cabinet and announce the referendum's date - possibly 24 June.

Some reports have claimed that Mr Tusk has been telling EU leaders that the talks could go on until Sunday. 

Meanwhile, Finance Minister Michael Noonan says he believes there would not be a land border in Northern Ireland if the UK leaves the European Union.

But Mr Noonan says it is vital not to have a barrier to trade just a few miles north of Dublin.

He says Ireland and the UK have legal agreements from before the existence of the EU, which would remain in place.

Tánaiste Joan Burton says it is important for Ireland that Britain stays within the EU, saying "our trade with Britain is worth billions of euro to Ireland".

Deal or no deal?

If Mr Cameron secures a deal and then a vote to remain in the EU, he will claim his strategy has been a triumph and hope the Conservative Party can stop "banging on about Europe", as he once said.

But if he gets a deal in Brussels that is then rejected by the British people in a referendum, he will come under enormous pressure to quit as Prime Minister immediately, despite claiming he would carry on if that happened.

And if there is no deal at this summit, there will almost certainly be no referendum in June.

One senior UK official described the gathering as "crunch time" for Mr Cameron.

Britain's renegotiation will not be the only major item on the agenda in Brussels, however.

Europe's migration crisis will be uppermost in many leaders' minds, with 2,000 migrants a day arriving in Turkey and Greece in the winter months and fears that the push on Aleppo in Syria could make matter worse.

Lengthy discussions in Brussels on migration could delay a deal on Britain's new membership deal.