The government offered unions a revised deal on public sector pension reform on Wednesday, but unions said it was not enough to avert a national strike planned for later this month.

Unions representing more than 2 million workers have been locked in a dispute with the government over its plans to raise pension contributions as part of austerity measures to tackle the budget deficit.

Treasury minister Danny Alexander met union leaders on Wednesday before announcing an offer in which workers would build up their pensions 8 percent more quickly than under previous proposals, while workers within 10 years of retirement would see no change to their pension.

The government's offer included a pledge not to revisit any agreed reforms within the next 25 years.

I hope on the basis of this offer, the trade unions will devote their energy to reaching agreement and not to unnecessary and damaging strike action, Alexander told parliament.

The unions, planning a national one-day stoppage on November 30, said they welcomed the offer and would study it pending further talks but the deal was not enough to give workers confidence they would have a decent pension.

Mark Serwotka, leader of the country's biggest civil service union, the PCS, a left-wing union, gave the offer a cautious welcome. After six months of there not being a single move on anything, it is of course welcome that they've modified their proposals slightly, he told BBC Radio.

But ... if someone robbed you of 10 pounds and then decided it was very harsh and only robbed you of nine pounds you are still being robbed.

The government says pension reform is necessary because people are living longer, the system is no longer affordable and pensions are generous compared with those in the private sector.

The battle over pensions mirrors that being fought in a number of European nations saddled with high public debts and a greying population.

Unless and until further real progress is made in those negotiations and acceptable offers are made, unions remain firmly committed to continuing their preparations for a planned day of action on November 30, said Brendan Barber, general secretary of the Trades Union Congress.

Responding to Barber's statement, Alexander made an appeal for individual union members to study his proposals, adding there was no more money on the table.

He did not have a figure on how much the concessions in the revised pension deal would cost the government.

Of course there's a lot more to talk about ... But in terms of the overall amount of money that's available within these schemes, I would say this is the best that we're going to get, Alexander said.

Roger Seifert, professor of industrial relations at Wolverhampton University, said ministers had taken a calculated risk by appealing over the heads of union leaders to workers not to strike in the hope that the message would be heard.

The substance of the offer is quite minor: there is no big change in the three big areas which are increased contributions, longer working and less at the end, he told Reuters.

But it is highly significant in the fact that there has been some offer at all.

He said the government was under enormous pressure because of the euro zone crisis and that it really can't afford to have a wave of public sector strikes ... They really would quite like this to go away.

Almost a third of a million public sector workers will lose their jobs under government austerity measures and millions of teachers, nurses and doctors are facing a pay freeze.

Prime Minister David Cameron threw his weight behind Alexander's plans. Low and middle income earners will be actually getting more from their public sector pensions. Everyone will keep what they have built up so far, he told parliament.

At the end of all this, people in the public sector will actually still get far, far better pensions than people in the private sector.

(Editing by Robert Woodward)