Three days before the arrival of Secretary of State Alexander M. Haig Jr., China tonight issued its strongest and most explicit opposition to U.S. arms sales to Taiwan, warning of a "destructive effect" on Sino-American relations.

In what is seen as a signal of Peking's resolve on the issue, the official New China News Agency said that "further strategic relations" between Peking and Washington depend on U.S. willingness to stop developing all contacts with Taiwan that go beyond nongovernmental relations.

"For the moment," said the sharply worded commentary, "the outstanding issue is about the U.S. arms sales to Taiwan."

Although some influential Chinese foreign policy specialists have indicated privately that China's leaders will take a more flexible stance when Haig begins his visit here Sunday, Peking has taken pains in the last few days to stress its opposition to all U.S. weapons sales to Taiwan.

Diplomats here believe the hard line Peking has voiced in recent public statements is designed in part to shore up its bargaining position for the Haig talks. The pointed warnings may also seek to counter what the Chinese regard as the strong influence of the pro-Taiwan wing of the Republican Party in Washington, diplomats speculated.

The news agency report, which also was broadcast on Radio Peking tonight, said any attempt by Washington to "lure" China into compromising by offering sophisticated weapons to Peking in exchange for its consent on sales to Taiwan is "doomed to failure."

The commentary also stressed that Peking is opposed to a continuation of current levels of U.S. arms sales to Taiwan. Taiwan now purchases between $700 million and $800 million worth of U.S. weapons a year.