TOKYO (Kyodo) -- Prime Minister Shigeru Ishiba said Friday that he is exploring the possibility of a telephone conversation with U.S. President Donald Trump, saying his imposition of reciprocal tariffs is a looming "national crisis" that requires an "unprecedented" response.

During a parliamentary session, Ishiba said the government should decide the most effective response to the planned 24 percent tariff levied on Japan, leaving the door open to possible retaliatory steps or taking the issue to the World Trade Organization.

Underscoring the serious impact the tariffs could have on Japan's export-driven economy, he again expressed his disappointment and regret that Trump announced the levy on the country's products entering the United States despite Tokyo's request for exemptions.

"This is a situation that can be called a national crisis," Ishiba told a session of the House of Representatives.

Ishiba, who heads the ruling Liberal Democratic Party, met with the leader of its junior coalition partner Komeito and opposition party heads to discuss how to respond to the move by the United States, Japan's close ally.

Ishiba was urged by Yoshihiko Noda, the chief of the Constitutional Democratic Party of Japan, the main opposition force, to meet the U.S. president face-to-face, participants in the meeting said.

The Japanese leader said he is ready to meet with Trump directly over the tariff issue if needed, seeking opposition support for making time in the parliamentary schedule should he or his Cabinet ministers need to travel to the United States.

The tariff announcement by Trump has roiled global financial markets and fueled concerns about slowing economic growth. Japanese stock prices have tanked and the yen spiked relative to the U.S. dollar, reflecting growing market anxiety.

According to one estimate, the tariff measures, including one on Japanese vehicles, would push down Japan's economic growth, as measured by inflation-adjusted gross domestic product, by 2.9 percentage points in the medium term.

A 25 percent additional duty on U.S.-bound vehicles would deal a heavy blow to Japanese automakers due to the importance of the U.S. market to their profits.