The official, who was present at Tuesday's meeting of the National Assembly Standing Committee on Defence which was briefed by the Navy, said the deal to buy the diesel-electric submarines would likely be signed by Chinese President Xi Jinping when he visits, "but that is still not final".
 Xi was due to travel to Pakistan this month, the government in Islamabad has said. China has said Xi would visit this year, but given no timeframe.
China and Pakistan call each other "all-weather friends" and their close ties have been underpinned by long-standing wariness of their common neighbour and rival, India, and a desire to hedge against U.S. influence across the region.
"The Prime Minister has approved buying eight submarines from China and these would be used to bolster Pakistan's strength," the official, who asked not to be identified, said.
He added that "last-minute homework is pending".
"Some officials are travelling to China even today. Work is ongoing," he said. "This deal is years in the making."
He said Pakistan was looking at S20 and Yuan class diesel-electric vessels.
A former senior Pakistan navy officer with knowledge of the negotiations told the Financial Times the contract could be worth USD 4 billion to USD 5 billion.
Asked about the submarines, Chinese Foreign Ministry spokeswoman Hua Chunying said China and Pakistan were friendly neighbours and that the two sides had normal military exchanges.
"I can tell you, relevant cooperation does not violate international convention and accords with China's three principles on military exports," she said.
China is Pakistan's top supplier of weapons, according to the Stockholm International Peace Research Institute (SIPRI), which tracks global arms sales, selling 51 percent of the weapons Islamabad imported in 2010-2014.
China has also surpassed Germany to become the world's third largest arms exporter, SIPRI said in a report last month. Little is known about China's arms exports because the country does not publish data on such sales.
The Pakistani official also said that Pakistan had been in talks with France to buy new submarines, but the proposal was declined by the French.
A top US Navy admiral said in February that, though they were technologically inferior, China's submarine fleet now outnumbered that of the United States.


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