The resignation of Apple Inc CEO Steve Jobs has opened the door for rival Samsung Electronics at a crucial time in the battle for smartphone supremacy in salesrooms and courtrooms around the world.

Jobs passed the reins to his right-hand man Tim Cook Wednesday, saying he could no longer fulfill his duties, raising fears the health of the Silicon Valley icon had worsened.

While Apple and analysts highlighted Cook's experience, as well as Jobs' new role as chairman and the company's extensive management bench, his departure will cause ripples across the Pacific at South Korea's Samsung.

More than any other firm, Samsung's fortunes are tied to Apple, both as a competitor and supplier of components.

The companies are fierce rivals, with Samsung's Galaxy range of smartphones and tablet computers running on Google's Android operating system seen as the main competitor to Apple's game-changing iPhones and iPads.

Even before Steve Jobs' (resignation), Samsung was getting more and more optimistic that they can actually take on Apple in the smartphone arena, Mark Newman, a former director of strategy at Samsung, where he worked for six years, told Reuters.

The game is really now Samsung's to lose ... They are picking up market share because of the change in dynamics in the smartphone industry, added Newman, now a senior analyst for global memory and consumer electronics at Sanford C Bernstein.

BOOMING MARKET

The Korean giant has taken big strides and is backing itself to unseat Apple.

When Samsung group executives asked Hong Won-pyo, executive vice president of Samsung's mobile division, at their weekly meeting on Wednesday if Samsung could overtake Apple in the smartphone market any time soon, he told them he was confident , according to a person at the meeting. Hong was speaking just hours before Jobs made his announcement to quit as CEO.

Apple and Samsung are scrapping for top spot in the smartphone market, having overtaken the market leader for the past decade, Finland's Nokia, in the second quarter.

Samsung's smartphone sales soared more than 500 percent in the second quarter, easily eclipsing Apple's 142 percent growth, though Apple sold about 1 million more units. Nokia sales fell 30 percent.

News of Jobs' departure helped Samsung shares rise 2.5 percent in Seoul Thursday. The broader Korean market was up 0.6 percent.

Investors were concerned that Apple would encroach into Android's turf, but Jobs' exit offers opportunities for Samsung to expand its smartphone market share at a time when Nokia is struggling, said Jeon Nam-joong, a fund manager at Consus Asset Management, which owns shares in Samsung.

Samsung still trails badly in tablet sales, where Apple racked up 14 million iPad sales in the first half, versus analysts' sales estimates of about 7.5 million Samsung tablet products for all of 2011.

Some expect that dominance to fade against rivals such as Samsung and LG Electronics

Apple's earnings will peak out with smartphones and tablets, said Jung Kyun-sik, a fund manager at Eugene Asset Management in Seoul, who argued the company didn't have great products to take on the baton from the iPhone and iPad.

Samsung and LG have been in the mobile hardware manufacturing industry over a decade and they'll lead the pack once Apple peaks out.

SOFTWARE PUSH

Samsung may also move more aggressively in closing the gap in software, one of its weakest links, after Chairman Lee Kun-hee asked the firm's top managers recently to come up with various measures, including mergers and acquisitions, to raise its software prowess, according to South Korean media.

Lee has been obsessed with raising Samsung's competitiveness by deepening its patent pool, talent and software abilities and might be tempted to look more closely for opportunities to take on Apple in earnest.

But the South Korean conglomerate also supplied Apple with about $5.7 billion in components last year, some 4 percent of Samsung's total sales.

Apple's portion grew to 5.8 percent of Samsung's sales in the first-quarter, driven by booming iPad and iPhone sales, which Samsung supplies chips for, along with Japan's Toshiba.

Samsung and Apple, along with many of the other players in the fast-growing mobile devices market, are also engaged in a costly and acrimonious patent and copyright battles around the globe.

Just on Wednesday, Apple won a preliminary injunction in a Dutch court stopping Samsung from marketing three smartphone models in some European companies.

It's difficult to gauge precisely what the impact will be as our relationship with Apple is very complicated and intertwined with so many parts of our business, said a senior executive at Samsung's general management division, who requested anonymity, given the sensitivity of the matter.

Bernstein's Newman agreed.

It's a very complex relationship and I think that it's very important to note that not only are they competitors, fierce rivals in the market place, but they need each other. I would say that Apple needs Samsung more than Samsung needs Apple.

(Reporting by Ju-min Park and Hyunjoo Jin in Seoul, Tim Kelly and Ayai Tomisawa in Tokyo, Clare Jin in Taipei, Cathy Yang in Hong Kong; Writing by Lincoln Feast; Editing by Dean Yates)