By William Schomberg and Kylie MacLellan
LONDON (Reuters) - Britain plans to increase the number of stealth fighter jets it can launch from aircraft carriers over the next decade and boost anti-terrorism spending by 30 percent, finance minister George Osborne said on Sunday.
Osborne is due to announce on Wednesday the details of spending cuts which, according to International Monetary Fund data, rank as the most aggressive austerity plan among the world's rich economies between now and 2020.
Ahead of that, the government will on Monday set out a five-year defense strategy.
"We are going to step up the aircraft carrier punch of the United Kingdom. We are going to make sure that when these aircraft carriers are available they are going to have planes that can fly from them in force," Osborne told BBC television.
"By 2023, we will be able to have 24 of these jets, some of the most powerful in the world, the F-35, on the decks of these carriers."
Those will be the first tranche of a total order of 138 of Lockheed Martin's F-35 Lightning II jets, a spokesman for the Ministry of Defence said. Britain had not previously confirmed how many it planned to order or a time scale, but the spokesman said the 24 marked a "substantial acceleration".
Osborne denied his overall focus on cutting public spending might hurt Britain's attempts to prevent attacks like the ones seen in Paris earlier this month, saying spending on anti-terrorism defenses would be increased by 30 percent.
"We will make sure that Britain is properly defended against the terrorist threat," he said.
Britain, which said in July it would commit to NATO's defense spending pledge of 2 percent of GDP for the next five years, had reduced defense spending by about 8 percent in real terms since 2010 to help cut a record budget deficit including shrinking the size of the armed forces by around one sixth.
As part of Wednesday's spending cuts announcement, the government will tweak plans to make big savings in Britain's welfare budget after an original proposal to scale back tax credits for lower-earning households was rejected in a rare rebellion by the upper house of parliament.
Osborne said on Sunday he was willing to listen to what he described as the "perfectly legitimate concerns" of those who have argued more must be done to ease the transition period.
He also said he was still aiming to return Britain to a budget surplus by the end of the decade but declined to confirm he would stick to a target of 10 billion pounds set out in July, saying the precise level would be announced on Wednesday.
"There is nothing painful about a surplus, the pain comes if you borrow forever, if you don’t fix your national finances," he said.
(Editing by Catherine Evans)