LONDON (PTI): The UK needs a bolder and stronger armed forces prepared to use "hard power" or risk being seen as a "paper tiger", Defence Secretary Gavin Williamson warned on Monday, amidst China flexing its muscles in the Indo-Pacific region.

Speaking at the Royal United Services Institute, he said Britain must stand up to those who "flout international law".

He also said the country's planned exit from the European Union on March 29 had brought the UK its "greatest opportunity" to strengthen its global presence.

Williamson detailed plans to modernise the armed forces, and said it must increase its "mass and lethality".

He revealed plans for two military ships that could be deployed for crisis support as well as military operations, the BBC reported.

He said they would be able to respond "at a moment's notice" to support the Royal Marines.

He also confirmed the Royal Navy's new aircraft carrier HMS Queen Elizabeth is being deployed to the Pacific region, where China has been involved in a dispute over territorial claims in the South China Sea.

The carrier will take part in the mission along with F-35 jets from the UK and US.

China claims nearly all of the South China Sea, though Taiwan, the Philippines, Brunei, Malaysia and Vietnam all claim parts of it.

Over the last five years China has rapidly built artificial islands housing significant military infrastructure on what had been low-lying reefs.

Williamson also said the country's cyber forces will be reinforced to defend and launch attacks.

With the boundaries between peace and war becoming "blurred", particularly by Russia and China, Williamson said Britain and its allies had to be ready "to use hard power to support our interests".

He told those gathered for his speech that "state-on-state competition was reviving".

The defence secretary said Russia is "resurgent" and rebuilding its military arsenal, adding that China is also developing its modern capability and commercial power.

"We have to be ready to show the high price of aggressive behaviour. Ready to strengthen our resilience," he said.

Defending interventionist policy, he said the cost of failing to act in global crises had often been "unacceptably high", and that Western powers cannot "walk on by when others are in need".

"To talk but fail to act risks our nation being seen as little more than a paper tiger," he added.

Williamson said Brexit brought an "unparalleled opportunity" to consider how the UK could maximise its influence around the world.

He said the UK would build new alliances and rekindle old ones, and shared his belief that Britain "should be the nation that people turn to when the world needs leadership".

But shadow defence secretary Nia Griffith said the UK's ability to play such a role had been "completely undermined by eight years of Tory defence cuts".

"The Conservatives have slashed the defence budget by over 9 billion pounds in real terms since 2010 and they are cutting armed forces numbers year after year.

"Instead of simply engaging in yet more sabre-rattling, Gavin Williamson should get to grips with the crisis in defence funding that is happening on his watch," she said.