WASHINGTON — The U.S. is sending an aircraft carrier group to the Middle East ahead of schedule and warning that Iran and its proxy forces are showing “troubling and escalatory” indications of a possible attack on American forces in the region.

Exactly what prompted the action was unclear, but it marked a further step in sharply rising tensions between the Trump administration and the Islamic Republic.

National Security Adviser John Bolton said Sunday night the U.S. was deploying the USS Abraham Lincoln Carrier Strike Group and a bomber task force to the Middle East, intending to send a message that “unrelenting force” will meet any attack on American forces or allies.

“The United States is not seeking war with the Iranian regime, but we are fully prepared to respond to any attack, whether by proxy, the Islamic Revolutionary Guard Corps or regular Iranian forces,” Bolton said.

U.S. officials would not provide any details about the supposed threat, which comes as the Trump administration wages a campaign of intensifying pressure against Iran and nearly a year after it withdrew from an Obama-era nuclear deal with Tehran.

In Iran, the semi-official ISNA news agency on Monday quoted an anonymous official as saying that Iranian President Hassan Rouhani planned a broadcast address Wednesday and might discuss “counteractions” Tehran will take over America’s withdrawal from the international nuclear deal.

The agreement limited Iran’s enrichment of uranium amid Western concerns that Tehran’s program could allow it to build nuclear weapons. Iran insists its program is for peaceful purposes.

The U.S. is trying to get Iran to halt activities such as supporting militant activities that destabilize the Middle East and threaten U.S. allies, including Israel, Secretary of State Mike Pompeo said.