The Canadian ambassador to the United States said yesterday that the two countries are in "a dangerous period of creeping confrontation" and need to "cool it" before more serious conflict erupts.

Ambassador Peter M. Towe told reporters that the United States could "shoot itself in the foot" if the Reagan administration carries out retaliatory action against Canada in response to Canadian steps to reduce American ownership of its energy industry.

Earlier this month, a senior Commerce Department official disclosed that a list of possible trade sanctions against Canada was being prepared at the request of the Reagan Cabinet.

"We're letting them know there is serious concern, not just in Congress but also in the administration, and they can't count on the administration to stand between Canada and Congress," Raymond J. Waldmann, assistant secretary of commerce for international economic policy, said.

Towe said he believed "responsible people within the administration want to find a way to contain these pressures" for retaliation, but he warned against the consequences of the United States "trying to throw its weight around."

The controversy centers on the year-old policy of the Canadian government to reduce foreign ownership of Canadian energy companies from 72 percent to 50 percent by the end of the decade. U.S. firms are the principal outside owners affected.

Asserting that sales have been on profitable terms for the U.S. owners, Towe said, "I don't think it's in the interest of the United States to hold the hands of the multinationals operating in Canada."

He pointed out that the United States enjoys a favorable $5 billion trade balance with Canada, its largest trading partner, and said that any effort "to punish Canada for its alleged sins" inevitably would backfire against the United States.