The economic tension between the United States and China escalated on Friday, as the Obama administration pledged to investigate Beijing’s subsidies to its growing clean energy industries while delaying a politically volatile report on the Chinese currency.

The approach  part carrot, part stick  reflected the delicate balance the administration is trying to strike in a campaign year by taking a newly assertive posture over China’s trade and commercial policies, while pursuing delicate negotiations as an alternative to confrontation.

Hours after the Office of the United States Trade Representative announced an investigation into China’s support for makers of wind and solar energy products, advanced batteries and energy-efficient vehicles, the Treasury Department said it would delay its semiannual report on foreign-exchange rates, which was due Friday, and could be critical of Beijing’s efforts to keep its currency artificially low.

The Treasury delayed the last such report, due April 15, until July 8.

The United States last branded China a currency manipulator, a designation that could lead to retaliatory tariffs, in 1994. Successive administrations have since declined to do so, arguing that it would be counterproductive. But as China has been blamed for a loss of American jobs, members of Congress, and now administration officials, have become increasingly critical of Beijing’s reluctance to permit greater exchange-rate flexibility. In June, Beijing agreed to do so, but then balked.