President Reagan said yesterday he would not encourage corporations to resume trade with Iran at this point.

The president told a news conference he understood a desire to eventually resume business with Iran, but he joked about the need to do business "long distance" to ensure business officials' safety and then answered with a flat "no" when asked if he would encourage business relations with Iran right now.

The answers came against a backdrop of continued uncertainty over when the trade embargo imposed lst April may be totally lifted. Former president Carter signed an order technically lifting the embargo before he left office, but President Reagan is reviewing that and other executive orders related to the agreement that led to freedom of the hostages.

While that review is underway, the legality of resuming trade and other issues are fuzzy. Most companies which previously traded with Iran have adopted a supercautious stance, postponing any decision until circumstances are clearer in spite of calls from Iran.

In the interim, corporations also may be able to measure the benefits of trade with Iran against the drawbacks, including having to contend with still-seething hostility to Iran on the part of many Americans.

Earlier this week, an employe of Watts Regulator Corp., a medium-sized company in Lawrence, Mass., said that the firm would like to start supplying Iran again with safety and control valves for heating and plumbing.

Watts officials, who said that the employe's statement did not represent the company's official position, immediately began to receive calls and abuse from people upset at the notion that a company would want to trade with Iran.

"Before Watts could even consider supplying its valve products to Iran, the federal government must officially clarify its position and fully sanction exports to Iran by U.S. companies," the company said yesterday in an official statement.

"Given such a basic precondition, Watts would only then consider whether or not there could be an eventual basis for a return to reasonable U.S. trade relations with Iran."

"That's our position, and we wouldn't dare do anything else. We couldn't morally, business-wise or in any other sense," said Senior Vice President Robert J. Tesar.

Tesar said that following publication of the story quoting the company's export manager, who he described as new to the company and not familiar with its operations, the company had gotten several dozen calls. In response, Watts Regulator sent mailgrams to its representatives and posted notices on bulletin boards in six plants describing its official position.

The company also has begun to receive critical mail, including one letter suggesting an alternative use for the company's valves.

"It's really caused us a lot of grief," Tesar said.