Latest threats to maritime power: The targets set in Options for Change are clearly not final. Christopher Bellamy reports

THE Government's announcement on Thursday night that Royal Navy strength would be reduced by a further 5,000 below the Options for Change target of 55,000 has focused attention on a new round of defence cuts, now called 'post-Options' by Ministry of Defence officials. In addition to reductions in the regular Navy, the Royal Naval Reserve is under threat of cuts below the Options target of 4,700.

The Navy also faces the loss of a vital component of British maritime power, which could never be replaced, according to senior officers. Proposals to sell the four newest Upholder-class conventional (diesel-electric) submarines to Canada were leaked earlier this year, and these - the Navy's only non-nuclear-powered submarines - remain at risk after the reprieve of the new commando helicopter carrier, announced on Monday.

Nuclear-powered submarines can remain submerged for much longer than conventional ones. But the latter are quieter and smaller, and have advantages in shallow water and for Special Boat Service commandos.

The Options for Change plans envisage a force of four Trident ballistic-missile firing submarines, 12 nuclear-powered attack submarines and four conventional submarines. Naval sources are adamant that a four- boat conventional submarine force is the absolute minimum. Meanwhile, 70 countries have conventional submarines and Iran has just acquired a Russian Kilo-class boat.

The Army and RAF could also face cuts beyond the Options 1995 threshold. Army strength, due to be reduced to 116,000, is now being held at 119,000, but after 1997, when Hong Kong is handed to China, the number of battalions might be further cut.

The RAF is to be reduced from a 1990 strength of 89,000 to 75,000 by 1995. Yesterday, the MoD rejected speculation that there could be a further reduction to below 70,000. 'So far the Government has only announced 75,000,' an RAF spokesman said.

Clearly, Options targets are not final. 'It's a continuing reassessment of the manpower requirements', an MoD Navy department official said. 'There are no operational implications.'

There are operational implications, however, of cuts to big equipment programmes, which are necessary to shave pounds 1bn off the defence budget over the next two years.

The reprieve of the Navy's new pounds 170m commando carrier, the landing platform helicopter, guarantees 1,500 civilian shipyard jobs for four years and safeguards what is probably the Navy's most immediately useful weapon. It can put 500 highly trained Marines ashore anywhere in the world - but it will have to be paid for.

The Royal Naval Reserve is due to be reduced from 5,900 to 4,700. Fears have been expressed that the RNR might be abolished, but MoD sources yesterday ruled that out.

'There is a study into the future structure of the RNR, and that could mean further cuts', a source said, 'but total wind- down is not a runner'.