China has begun to account for more than half the American trade deficit in some months, including last November, partly because of rising production of shale gas and shale oil that has reduced America’s need to import energy. China was only a quarter to a third of the American deficit before the global financial crisis began in 2008. As the American economy continues to improve, economists predict that Americans will import even more from China.

“The pickup in China’s trade surpluses could lead to rising trade tensions if they are perceived as holding back job growth in the U.S. and dampening the economic recovery,” said Eswar Prasad, a Brookings Institution economist specializing in China.

The gradual recovery in demand in the United States and Europe is being partly absorbed by Chinese exporters instead of stimulating longer hours and further investment at factories closer to home. The unexpected strength in China’s export sector has weakened the West’s economic recovery and retarded job creation in the United States and Europe.

Asked this week for their view on China’s trade surpluses, United States Treasury officials reiterated their opinion that the renminbi, China’s currency, remains significantly undervalued, which China denies, and said that rebalancing the Chinese economy remained incomplete.

The composition of the American trade deficit with China is also shifting in ways that could affect employment in the United States, according to the latest American data, released on Tuesday. The American deficit is increasingly in goods classified by the United States Commerce Department as advanced technology products, notably consumer electronics, while starting to shrink in categories of lower value like shoes.

Chinese leaders and some economists have contended for years that a decline in China’s export competitiveness is imminent, but their country has continued to post trade surpluses. They have used their predictions of slowing exports to justify resistance to pressure from Washington for faster appreciation of the renminbi against the dollar. The renminbi rose only 3.1 percent against the dollar last year, and weakened 1.2 percent against the euro.

The question is how much longer China can remain the dominant exporter. Many economists still predict trouble ahead for Chinese exporters. “Even if there is an increase in the trade surplus, this is temporary,” said Diana Choyleva, a China specialist who is the head of macroeconomic research at Lombard Street Research in London.