China should loosen restrictions on imports of agricultural products and the move would help to speed up the conclusion of bilateral investment treaty negotiations with the United States, a former deputy trade minister said on Tuesday.

"During the recent National People's Congress a deputy proposed further opening imports of agricultural products, except for rice and wheat. I totally agreed with him," Long said at an event hosted by the Center for China & Globalization, a think tank.

In the 1990s, Long was the chief negotiator of China's accession to the World Trade Organization, and is now the chairman of the advisory commission of the Center for China & Globalization.

"A global perspective is needed to address the nation's environmental problems. China's farmland has been heavily polluted by fertilizers and pesticide. The land needs to take a breath," he said.

He also questioned China's "red line" of safeguarding 120 million hectares of arable land, an amount considered by mainstream opinion as a minimum to ensure China's food security. "China's is a bit conservative in agricultural issues," he said.

Long suggested that relaxing restrictions on agricultural product imports could gain China more leverage in international negotiations.

"Agricultural product protection is already the toughest issue in China-US negotiations…if you concede a little on this issue to the Americans, they could make concessions on other issues," he said, referring to the bilateral investment treaty China is negotiating with the US.