By Michael Bristow
BBC News, Beijing
China will never have Western-style democracy, a senior official said as the country began its most important political meeting in five years.
Mr Li said reforms would instead help improve "socialist democracy"
But Li Dongsheng, spokesman for the Communist Party's 17th congress, said China would pursue political reform.
Chinese leader Hu Jintao addressed more than 2,200 delegates as the congress opened in the capital on Monday.
Some party members have called for political changes to accompany economic reforms, which have transformed China.
Mr Li said: "Political reform is an important component of our comprehensive reform. We have advanced political reform without pause."
But he quickly quashed any idea that China could eventually become a multi-party liberal democracy.
"We will never copy the Western model of political system," he said as he gave details about the congress, which meets every five years.
Mr Li's statement is not surprising as other senior party leaders have voiced similar comments in the past.
But it sets the tone for the congress, at which delegates will endorse policies that are set to shape China over the coming years.
The 17th Communist Party congress is a major event in China
As well as discussing future policies, congress delegates will hear a report from President Hu, who is also the party's general secretary.
They will also amend the party's constitution to reflect what Mr Li described as "theoretical innovations".
That probably means President Hu's ideas about "scientific development" will be written into the constitution.
This concept calls for more balanced economic development that does not lead to problems such as pollution or a widening wealth gap between rich and poor.
The constitution was also changed in 2002 to include previous President Jiang Zemin's contribution to political thought - The Three Represents.
That idea reflected the former president's desire to bring a wider range of people into the party, most notably China's newly rich business class.
At the press conference, Mr Li revealed that ex-President Jiang, as well as two former premiers, Li Peng and Zhu Rongji, will attend the congress as special delegates.
These veteran leaders will join a total of 2,213 ordinary delegates.
Tight security is being put in place in Beijing ahead of the congress
The delegates' main task will be to select the party central committee, which will then in turn select members of the politburo, the country's highest decision-making body.
There has been widespread speculation about who will be elected to the politburo's elite standing committee.
Li Keqiang, the current chief of Liaoning Province, and Shanghai boss Xi Jinping have both been tipped to join the standing committee.
But whatever policies and personnel changes are approved at the week-long congress, China is set to continue on its current course.
The congress' spokesman, Li Dongsheng, dismissed discontent about problems such as pollution and the illegal taking of farmers' land.
He said these were regional and individual cases.
"The majority of people have enjoyed real benefits from reform and opening up," he said.