With its Iranian oil supplies being choked off, Japan today began to search for other oil sources and is considering asking the United States for help.

Angry at Japan's refusal to go along with a $2.50 per barrel price increase, Iran's national oil company Sunday shut off supplies to one major Japanese importer and was reportedly preparing to cut off the others.

Japan became the second country, after Portugal, to be punished with an Iranian oil cutoff for supporting American efforts to pressure Iran to release U.S. Embassy hostages.

Even before confirmation of the cutoff reached Tokyo tonight, chief Cabinet secretary Masayoski Ito said it was possible Japan would ask American oil companies to sell more oil here.

The Japanese government was also reportedly preparing to ask the International Energy Agency for emergency assistance.

Japan buys between 10 and 12 percent of its total oil imports from Iran. Officials expressed optimism that the shortage would cause no immediate problems but said they were concerned about the long-term dangers.

Ito told reporters Japan would first meet the problem by new oil conservation measures and by tapping reserves sufficient to last 85 days if all imports from other countries ceased.