Last month, a report - which included alleged satellite imagery and intelligence said to be provided by informants working covertly inside the Iranian military - indicated the Iranian regime is secretly, and illegally, developing weapons at its "off-limits" Parchin nuclear site.
Coats appeared before the Senate committee along with other intelligence agency leaders, including CIA Director Mike Pompeo and National Security Agency Director Mike Rogers.
In addition, Coats said that "Russia is likely to be more aggressive in global affairs, more unpredictable in its approach to the USA".
Mr. Trump has repeatedly denounced as "fake news" the accusations that members of his circle colluded with Russian Federation.
"We have dedicated a very significant amount of our intelligence resources to the issue of North Korea".
Iran is continuing to work on ballistic missiles that would be capable of carrying nuclear weapons over thousands of miles, according to US Director of National Intelligence Daniel Coats.
"The intelligence suggests we're going to need more to shake free this terribly challenging problem".
The U.S. and South Korea Launch Operation Max Thunder Thu, April 20, 2017 The US and South Korea kicked off a big exercise just as North Korea threatens "thermonuclear war".
"They are on that path and they are committed to doing that", he said.
On Afghanistan, Coats said the situation "will very likely continue to deteriorate, even if worldwide support is sustained".
"Afghanistan will struggle to curb its dependence on external support until it contains the insurgency or reaches a peace agreement with the Taliban", Coats told lawmakers in presenting an annual assessment of threats to United States national security.
LTG Vincent Stewart, the Defense Intelligence Agency's director, also testified before a Senate panel on Thursday that the situation is grim and that the United States must do "something very different" in Afghanistan or else the Taliban will make new advances on the battlefield.
The Trump administration is considering sending 3,000 to 5,000 additional troops to Afghanistan to help train Afghan security forces. Stewart noted that North Korea has expressed the goal of creating an intercontinental ballistic missile (ICBM) tipped with a miniaturized nuclear weapon, and each test comes with progress towards that explicit goal.
The DPRK said early this month that the current crisis on the Korean Peninsula is the most unsafe in half a century since the 1950-1953 Korean War.
Coats told the committee that he seems Iran holding to the nuclear deal agreed to last year, and that the deal, which extended Iran's breakout time for a nuclear weapon from a few months to a year, has enhanced transparency of Iran's nuclear activities.