* Lead negotiators reach deal on 960 bln euro plan
* Socialist lawmaker in talks rejects agreement
* Unclear whether deal will pass July vote in EU parliament
Negotiators reached a provisional deal on Wednesday to finalise the European Union's 960 billion euro long-term budget, but ratification of the deal was immediately thrown into doubt by a leading socialist lawmaker in the talks.
The deal between representatives of EU member states and the European Parliament on a seven-year spending package needs majority support from the parliament to come into force as planned at the start of 2014.
But the head negotiator for the Socialist group in the parliament - the second largest group - said he was not satisfied with the outcome.
"Negotiations concluded. Not satisfactory to all. We cannot confirm agreement tonight," Bulgarian socialist MEP Ivailo Kalfin tweeted after the talks.
Without the support of the socialist group, it is unclear whether the deal will pass a parliamentary vote scheduled for early July. Further talks among MEPs and governments may be needed to secure majority backing, EU officials said.
That could delay the start of EU development funding for poorer regions hit by recession, as well as a new initiative to combat rising youth unemployment in parts of the 27-nation bloc.
Irish Deputy Prime Minister Eamon Gilmore, who represented EU governments in the talks, said he would ask EU ministers to endorse the deal at a meeting in Luxembourg on Tuesday.
"We have concluded the negotiations. The lead negotiator for parliament and I have agreed a package that we are both going to recommend to our respective sides," he told reporters in Brussels after more than 24 hours of talks.
The deal left unchanged the overall spending limits for 2014-2020 agreed by EU leaders in February. They included the first ever real-terms decrease in long-term spending, while agriculture and development funding will continue to enjoy the largest budgets.
But negotiators did agree that a limited amount of unspent funds could be moved from one year's budget to the next, instead of being returned to national coffers as at present.
EU officials have said that, contrary to the spirit of the leaders' February deal, that change could mean increased spending over the next budget period compared to now, depending on the outcome of subsequent annual budget negotiations.