David Cameron's hopes of a deal on a new relationship between the UK and the European Union still face a number of hurdles, his Irish counterpart has suggested.
Taoiseach Enda Kenny said there were still "complications" in relation to the proposals, which will be considered at a crunch meeting of EU leaders in February.
But in a boost to Mr Cameron's reform agenda, Mr Kenny said the problems were "solvable" and he hoped it was possible a deal could be done at the summit in Brussels.
In a joint press conference in Number 10, Mr Kenny said European Council president Donald Tusk would publish a paper next week on the UK's four key areas of concern.
"I actually believe that all of these are solvable, in a really positive sense," he said.
Setting out his desire for the UK to vote to stay in the 28-member bloc, he said: "Europe will be much stronger with Britain as a central and fundamental member."
He added: "I have not seen President Tusk's paper yet and obviously the Prime Minister has pointed out himself his view on whether it's absolutely necessary that we should do it in February.
"My belief is that of the four issues that are on the table there, there are still complications with one or two of those.
"But I think these are issues which can be sorted and can be agreed.
"I would hope personally that it might be possible to do it in February but then I can't speak for all of the other countries around the table."
He called for businesses to speak out on the issue, highlighting the importance of reforming the EU to "work more effectively in the interests of greater trade, of trade agreements, the opportunity to cut unemployment, to create employment and so on".
Mr Cameron said: "Today we have discussed the areas where I have set out we need to see reform, on economic governance, on sovereignty and competitiveness and, of course, on welfare.
"The UK and Ireland share a strong desire to make the EU more competitive and to prioritise free trade agreements with the fastest-growing markets across the world.
"We are making progress in our negotiations and I am confident that with the right political will we can secure the reforms that will address the concerns of the British people."
The Prime Minister said there should be a focus on the "positive opportunity for Britain" of changes in the relationship with Brussels as he repeated his position that there was "plenty of time" to achieve a deal.
He said: "Imagine the scale of the prize if we can remain a member of the single market, with 500 million consumers, a quarter of the global economy, with a seat at the table and a say over the rules, making sure we do right by our business, for jobs, investment and growth in the UK.
"Combined with action to make sure we deal with the things that frustrate people about the EU."
Pressed on whether there would be a deal at February's European Council, Mr Cameron said: "It is possible for it to happen in February. If there is a good deal on the table, I'll take that deal, I'll take it to the British people and explain why it's the best of both worlds. But it has got to be the best of both worlds.
"It has got to be the right deal. If it is not there we've got plenty of time. We don't need a referendum until the end of 2017."
He added: "I have tried to approach this in a very sensible way throughout the last few months, travelling around Europe, explaining what needs to be done, putting very concrete and sensible proposals on the table.
"If all of those get a proper and sensible response, we can do this in February. But I would rather get it right than do it in a rush."
The Prime Minister's comments came after the leader of the campaign for the UK to remain in the EU pushed for a referendum as soon as possible after a deal is reached, following speculation a vote could be held as early as June.
Lord Rose, chairman of Britain Stronger In Europe, said his group would be ready for a June vote: "Once we have a deal, whenever that deal might be, let's assume it is in February, why would you want to wait?
"I think there is enough time to get the information out, to get the facts out, to have a healthy debate."