By Trevor Hunnicutt, Gram Slattery and Steve Holland

WASHINGTON, April 1 (Reuters) - U.S. President Donald Trump told the nation in a televised speech on Wednesday night that the U.S. military had nearly accomplished its goals in Iran, but he declined to offer a concrete timeline for winding down the conflict.

Facing a war-wary American public, sliding approval ratings and pressure from some allies to outline his war aims in more precise and consistent terms, Trump said the U.S. had destroyed Iran's navy and air force, and crippled its ballistic missile and nuclear programs.

He added that the U.S. would continue to hit targets in the Islamic Republic over the next two to three weeks, and assured viewers that the U.S. would finish the job "very fast."

But he glossed over some unresolved issues that remain during his 19-minute speech, such as the status of Iran's enriched uranium and access through the Strait of Hormuz, a conduit for global oil supplies which Iran has effectively closed since the U.S. and Israel launched the war on February 28.

And he notably suggested the war could escalate if Iranian leaders did not capitulate to U.S. terms during negotiations, with strikes on Iran's energy and oil infrastructure possible.

He asked Americans to keep perspective about a war now in its fifth week, pointing out that the conflict was much shorter than the country's involvement in several previous wars.

"I can say tonight that we are on track to complete all of America's military objectives shortly, very shortly. We're going to hit them extremely hard over the next two to three weeks. We're going to bring them back to the stone ages where they belong," Trump said.

"In the meantime, discussions are ongoing... The new group is less radical and much more reasonable. Yet if during this period of time, no deal is made, we have our eyes on key targets."

Trump and his advisers have offered shifting explanations and timelines for the conflict. Some allies are pushing the president to assuage growing concerns among Americans, most of whom oppose the conflict and are upset at rising gasoline prices due to disruptions in the global oil supply.

The president briefly addressed those concerns, mainly to say that gasoline prices would soon go down, that it was a worthwhile short-term sacrifice and that it was mainly Iran's fault.

"This short-term increase has been entirely the result of the Iranian regime launching deranged terror attacks against commercial oil tankers of neighboring countries that have nothing to do with the conflict," Trump said.

Reflecting widespread sentiment that Trump's comments did not portend a short-term off-ramp, stocks fell, the dollar firmed and oil rose shortly after Trump's comments.

Posted by: Alma Angeles/NET25 News