China's top tier cities may elevate themselves from regional centers to future global metropolises, with advantages in sectors such as smart cities and artificial intelligence.

International investors from global giants like Boeing, Merck and Siemens shared this view at the Annual Investment Conference in South China's Guangzhou on Wednesday.

The conference is a major event aimed at promoting the city to potential investors and listening to their comments on its business environment. Over 1,800 enterprises from around the world attended the conference.

Many investors stated that China is now more than just a large market for them.

This year China is celebrating the 40th anniversary of its reform and opening-up.

Merck, a world leading company in health care, life science and performance materials, has been operating in China for over 80 years. As well as its existing research and development centers and labs in Beijing and Shanghai, the company established a new China Innovation Center in Shanghai in February.

"The opening-up of China has made a great difference to our business and it allowed us to advance business sectors liquid crystal and pigments," said Allan Gabor, managing director of Merck China.

"When Merck looks at China, we see China as much more than a large business market, we see it actually as an enabler of our global strategy," Gabor added.

Similarly, John Bruns, vice president of Boeing International, said China is now "a source of innovation" from the company's perspective.

The American aviation giant will soon open its first finishing and delivering center for 737 planes outside the United States in East China near Shanghai, and recently signed an agreement with China Southern Airlines to initiate a 737 converted freight project in Guangzhou, and to include a local maintenance company in its 787 global care program.

Cities like Beijing, Shanghai, Guangzhou and Shenzhen, and the Greater Bay Area of Guangdong, Hong Kong and Macao, are becoming the key players in investors' global strategies.

These cities have mature urban infrastructure, advanced industries and are renewing their focus on development to be in line with the information revolution and an international lifestyle.

Guangzhou, for example, is focusing on the new generation of information technology, artificial intelligence, bio-pharmaceuticals, as well as new energy and new materials.

The output of its new generation internet technology and panel display industries have both exceeded 100 billion yuan. It is also ambitious in becoming a smart city, by teaming up with global giants like Cisco and Siemens.

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"A future global city should be leading in smart mobility and smart energy distribution and future technology like AI. I think Guangzhou is on a very good way to that," said Jens Hildebrandt, chief representative of Delegation of German Industry and Commerce Guangzhou.

But investors also pointed out that Chinese cities still need to tackle a series of challenges before they become global cities, including IPR protection, environmental protection, further opening-up and continuous innovation, as well as self promotion.

These are also the areas where huge opportunities lie.

Three months ago, SHV Energy, the world's largest distributor of LPG energy solutions, signed an memorandum of understanding with Guangdong province, to build a LPG terminal in the city's Nansha district.

"With the strong focus of the Chinese government to improve air quality and reduce emissions, you see a higher need for clean energy solutions." said Maarten Bijl, global vice president of the company.

He added that SHV is also innovating its business model and looking for cleaner energy solutions in which it can cooperate with the Chinese cities. "We're in discussion to see how we can work with the city of Guangzhou, and we can get hydrogen mobility solutions here, which is the next step."

Aside from the top tier cities, China as a whole is putting every effort to further open up. Earlier this month, the government pledged to continue to streamline administration and delegate power to improve the business environment and further stimulate market vitality.