The United States will confront a strengthening alliance and convergence of interests between rival powers Russia and China, just as policy changes made by the Trump administration may cause allies look beyond Washington, leaders of the U.S. intelligence community warned Tuesday.

"China and Russia are more aligned than at any point since the mid-1950s, and the relationship is likely to strengthen in the coming year," according to the 2019 Worldwide Threat Assessment, which was presented by the intelligence community's top brass at an annual hearing before the Senate Select Committee on Intelligence.

"At the same time, some U.S. allies and partners are seeking greater independence from Washington in response to their perceptions of changing U.S. policies on security and trade," the assessment warned.

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Security challenges faced by the country's intelligence and law enforcement agencies will also grow more complex as technological advances and explosions of data make analysis more daunting and the integrity of data more questionable, according to intelligence officials and key lawmakers.

In his opening remarks, Chairman Richard Burr, a North Carolina Republican, identified a theme, persistent throughout the hearing, that the country was traversing a "new age – a time characterized by hybrid warfare and weaponized information, all occurring within the context of a world producing more data than mankind has ever seen."

Among the areas that remain ripe for disruption, according to the intelligence officials, are U.S. elections, which Russia is known to have targeted in 2016, and which Vice Chairman Mark Warner, a Virginia Democrat, said both Russia and "unknown actors" targeted in 2018.

"Our adversaries and strategic competitors probably already are looking to the 2020 U.S. elections as an opportunity to advance their interests," the threat assessment said. "We expect our adversaries and strategic competitors to refine their capabilities and add new tactics as they learn from each other's experiences, suggesting the threat landscape could look very different in 2020 and future elections."

Some of the administration's policies – particularly vis-a-vis North Korea, Iran and ISIS in Syria – were thrown into stark relief as the intelligence officials offered assessments that departed from recent choices made by the Trump administration and statements made by the president.

"We currently assess that North Korea will seek to retain" its nuclear capabilities, said Director of National Intelligence Dan Coats, who was among the panelists and whose office issued the report. Coats noted the intelligence community had made "observations of some activity" that were "inconsistent with full denuclearization."

CIA Director Gina Haspel said the agency's analysts likely "value the dialogue" emerging between North Korea and the U.S., but likewise indicated Kim's intention to denuclearize remained undemonstrated.

In June, President Trump, returning from his first historic summit with North Korean leader Kim Jong Un, tweeted, "There is no longer a Nuclear Threat from North Korea." That summit resulted in a framework document that included "complete denuclearization of the Korean peninsula" as a goal but offered few details on its achievement.

A second summit between Mr. Trump and Kim is planned for late February, which itself comes after several, reportedly warm, epistolary exchanges between the two leaders.

Intelligence officials were also unified in their assessment of Iran's nuclear ambitions, which they said remained effectively checked by the Iran nuclear deal. The deal, known as the Joint Comprehensive Plan of Action, was struck in 2015 by the Obama administration; the Trump administration withdrew the United States from it last year, calling the agreement "defective."

"We do not believe that Iran is currently undertaking the key activities we judge necessary to produce a nuclear device," Coats indicated. "I think the assessments we've made up to this particular point hold."

"At the moment, technically, they're in compliance," Haspel said, though she noted Tehran is "considering taking steps that would lessen their adherence" to the deal – in part to pressure Europeans, who remain signatories, to help prevent its collapse.

The threat assessment also offered a view at odds with the president's recent decision to withdraw U.S. forces from Syria; Mr. Trump last month declared the United States victorious in its campaign against the Islamic State, also known as ISIS, and vowed to bring roughly 2,000 troops home.

"We have defeated ISIS in Syria, my only reason for being there during the Trump presidency," Mr. Trump tweeted in December.

Haspel, noting ISIS had suffered significant leadership losses and nearly all of the territory it once controlled, said the group was "still dangerous" as it commanded "thousands" of fighters in Iraq and Syria.

"This terrorism threat is going to continue for some time," Coats added, citing ISIS' still-pervasive ideology and the movement of its fighters to ungoverned spaces beyond Syria.

The committee's hearing began with its leaders offering condolences to the DIA and NSA, whose directors, Gen. Robert Ashley and Gen. Paul Nakasone, were also among the panelists – a DIA employee and a Chief Navy Cryptologic Technician were among those killed in Syria by a suicide bomber on January 16.

"This is a stark, sobering reminder of the dangerous work that the men and women of the intelligence community do around the world on behalf of this country, every single day – often with no public acknowledgement," Burr said.