HOUSTON -- Houston, the fourth largest US city, is intent on boosting its ties with China in all areas, the city's mayor Annise Parker has said.

"Houston has a long history with China, and we have close ties in a number of areas ... China is Houston's number one trading partner," she told Xinhua in a recent exclusive interview.

Trade between Houston and China totaled $12.9 billion in 2012, and that figure has increased by more than $11.3 billion since 2000, representing a compound annual growth rate of 19.45 percent, according to the Greater Houston Partnership (GHP), an economic development organization.

A growing number of Chinese manufacturers, attracted by Houston' s low tax structure and easy permitting environment, are opening plants there, she said.

Meanwhile, more and more companies based in Houston also extended their reach into China, she said. The GHP's figures showed more than 830 Houston companies operated 3,032 subsidiary locations throughout China in 2012.

Since taking office in 2010, Parker said she had tried to open a non-stop flight between Houston and China to facilitate transportation. Her efforts paid off in July this year when China' s national flag carrier Air China landed its maiden non-stop flight from Beijing at the George Bush Intercontinental Airport.

The non-stop flight is estimated to have an economic impact of nearly $150 million on the Houston economy alone, according to the GHP.

"I understand it is already a very popular flight and we hope the number of flights expands," she said.

Speaking of Houston's pro-business environment, Parker said Chinese companies are welcome to invest here.

"Houston is one of the most free market cities in the United States ... We are a city with a reasonable regulatory environment, and we are considered a very lightly-regulated city in terms of business. And we are also a city that works very hard to reduce or remove barriers to businesses that want to cooperate," Parker said.

"We would like Chinese businessmen and businesswomen to come to the United States, particularly in Houston. Now, we have this new non-stop flight and make sure that we have the opportunity to convince them that Houston is a great place for business," she added.

Parker said Houston is committed to expanding its cooperation and exchanges with China not only in business but also in culture and civil service. The past two years have seen exchanges between police departments, airports and libraries between the two sides.

Meanwhile, Houston, a sister city of China's southern trade hub Shenzhen, has forged close ties with many other Chinese cities, including Beijing and Shanghai, hometown of Houston's most celebrated Chinese Yao Ming, she said.

When asked about things that may hamper the bilateral ties, Parker said the complicated visa approving procedure of the United States is a major inconvenience for many Chinese.

"It is not within the control of local elected officials, but we need to make it easier for Chinese businessmen and businesswomen to receive visas. When the travelers are in transit, we need to make sure that they get through our airport as rapidly as possible. We have a good reputation with that, but we need to make sure that we maintain the reputation of being a good port entry to the United States," she said.