Apple is to make content from Google’s video-sharing site, YouTube available on television screens, marking another advance for one of the technology sector’s most formidable partnerships.

From mid-June, the Apple TV set-top box will stream clips uploaded on the YouTube site to a users’ televisions.

The move boosts the amount of content available through Apple TV. The wireless router, which flows online video content from computers to widescreen TVs, has so far received a lukewarm reception, with some analysts suggesting Apple may have lost its knack of creating blockbuster products in the wake of the iPod.

It could also expose Apple to the legal wrangle surrounding YouTube’s alleged use of bootlegged content. Google, which bought YouTube for $1.6 billion last year, faces a $1 billion lawsuit from Viacom. However, the media giant behind MTV struck a conciliatory tone today, suggesting that it would welcome the opportunity to work with Apple.

Apple and Google are already co-operating on a number of projects, with the Apple chief executive, Steve Jobs, using a rare meeting with Bill Gates, the Microsoft co-founder, last night to hype the version of Google’s Mapping service that will appear on Apple’s iPhone.

Eric Schmidt, the Google chief executive, sits on the Apple board.

Apple also unveiled an upgrade to the Apple TV device, introducing a model with a 160 gigabyte hard drive, four-times larger than previous versions and enough to store up to 200 hours of video, 36,000 music tracks or 25,000 photos. It will be available in the UK from June 1, for £269.

The upgrade, just 141 days since Apple TV was launched at the group's Macworld Expo in San Francisco, raised further question marks over whether Mr Jobs was satisfied with the original product. Observers have suggested that Apple TV will struggle until the device supports high-definition pictures, with some pointing out that in terms of picture and sound quality consumers would be better off opting for a humble DVD player.

Separately, Google unveiled technology that can keep online applications such as e-mail running on computers even if internet connections are disrupted or unavailable.

The search engine giant introduced the Google Gears tool at the opening of Google Developer Day 2007 in Sydney, Australia.

Designed to boost the appeal of web-based applications – accessed online – the free tool will pose a threat to traditional rival tools, such as Microsoft’s Word and Excel applications, which are run on a user's PC.

The browser extension downloads enough data to a computer to enable people to continue using web-based applications such as e-mail while out of range of the internet - such as on a flight.

Google plans to make the Gears technology available in an "opensource" format that will allow other developers to access the blueprints to the system to modify it.

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