A missile defense battle of wills is being waged in Congress over testing of a new interceptor missile that is to be deployed on Navy destroyers and could provide improved defense of Hawaii and the West Coast from North Korean threats.

The Democratic-led U.S. House of Representatives passed its version of the 2020 National Defense Authorization Act with language canceling the much-awaited first test of the new SM-3 Block IIA missile against an intercontinental range ballistic missile in 2020, and replaced it with a retest against an intermediate-range target.

The Block IIA missile, built by Raytheon, is faster and has more range compared with the current SM-3 Block IB, which is deployed on Navy ships positioned in places like Guam and Japan to guard against short- to intermediate-range North Korean missiles.

Whatever test is conducted in 2020 likely will occur at the Pacific Missile Range Facility off Kauai.

The Trump administration in a July memo said it “strongly objects” to the proposed House change as another flight test against the shorter-range target would “add little technical value” given that the Missile Defense Agency successfully tested an SM-3 Block IIA missile against a intermediate-range missile off Kauai in December.

The Senate does not have similar language in its defense authorization bill.

Democratic concern is that the new missile could accelerate the global arms race, defense experts say.

China, in particular, will be unhappy that Japan, which is co-developing the Block IIA variant with the United States, has the added capability.

Changing political leadership in Congress has affected missile testing priorities.

Under Republican control, Congress in the 2018 National Defense Authorization Act required the Missile Defense Agency to test the new Block IIA missile against an ICBM-class target by Dec. 31, 2020. Democrats won control of the House in last year’s midterm election.

Conferees are now working out the latest version of the bill.

Thomas Karako, a senior fellow with the International Security Program and director of the Missile Defense Project at the Center for Strategic and International Studies, said he thinks the Pentagon and Senate might override the House so a test against an ICBM target will still occur in 2020.

“So what this is about is trying to come up with more options and increased flexibility for the kind of contemporary North Korean-style ICBM threat,” Karako said. “So frankly, I think it’s the right thing to go out and test against this and see if it can be done.”

Karako said that “there’s just too many reasons to (test against an ICBM threat) and not enough reasons not to do it.” He added, “I just don’t think we’re going to get anywhere close to the kind of numbers (of Block IIA variants) that would really disrupt strategic stability.”

The Block IIA variant also is the centerpiece of a European missile defense system designed to counter Iranian missiles and will be deployed in Poland.

The new missile can be fired from the same Navy ship launchers as the SM-3 IB missile. The upgraded version has a uniform 21-inch diameter, rather than a tapered body, to accommodate more rocket fuel.

Greater speeds and ranges are needed to down ICBMs, which can reach speeds of more than 15,000 mph.

The Pentagon’s 2019 Missile Defense Review said the SM-3 Block IIA interceptor has the potential to provide an important “underlay” to the existing 44 ground-based interceptors in Alaska and California for ICBM missile defense of the United States, including Hawaii.

Japan, meanwhile, is eager for full production of the new missile to begin.

Even though a test of the new missile in December off Kauai succeeded in intercepting an intermediate- range target, some questions remain about the technology and testing.

The Government Accountability Office said the scope was reduced from an attempt against two targets to a single intercept because of a test range safety malfunction.

Riki Ellison, chairman of the Missile Defense Advocacy Alliance, said some officials want to retest the intermediate-range capability.

He said a single new test or a pair of missiles could test both intermediate- and ICBM-range capabilities in 2020.

“You don’t want to wait another year or two years to test it like we’ve been doing in the past,” he said. “This is where this is coming to a head.”