It’s now more than eight weeks since Senator Ted Cruz sent a letter to three senior officials of the Obama administration, detailing his concerns that North Korea and Iran might be working together on developing nuclear missiles.

In particular, Cruz had a question for Director of National Intelligence James Clapper. Referring to the period since the Iran nuclear deal took effect on Jan. 16, Cruz asked: “Has the U.S. intelligence community observed any possible nuclear collaboration between Iran and North Korea…”?

That’s one of the huge questions looming behind the Iran nuclear deal, officially titled the Joint Comprehensive Plan of Action, which President Obama has been urging President-elect Donald Trump to preserve.

It’s a question that deserves an immediate answer. If there has been any such nuclear teamwork between Tehran and rogue, nuclear-testing Pyongyang, that would be a violation by Iran that should immediately blow up the Iran deal — which the Obama White House currently touts on its web site as “The Historic Deal that Will Prevent Iran from Acquiring a Nuclear Weapon.”

Questions about possible Iran-North Korea teamwork on nuclear weapons are well-founded, as Cruz explained in his seven-page letter, referencing numerous open-source reports (including two of my own). North Korea and Iran have been strategic allies since just after Iran’s 1979 Islamic revolution. They have a long history of weapons deals, in which the usual arrangement has been that North Korea works on the weapons, oil-rich Iran pays the bills, and technicians shuttle between both countries.

While there’s been no official U.S. confirmation that this Iran-North Korea partnership extends to nuclear collaboration, there’s plenty of official U.S. documentation that it includes cooperation on developing ballistic missiles. That has long raised questions about whether the two countries are also in nuclear cahoots, because ballistic missiles are basically cost-efficient only as vehicles for delivering nuclear warheads.

And though it could be mere coincidence, it is striking that during the past year, in which Iran — to multi-billion dollar emolument — has officially relinquished any interest in nuclear weapons, cash-hungry North Korea has never been busier. North Korea has carried out two nuclear tests this year alone, in January and September, bringing its total number of nuclear tests to five since 2006, four of them during Obama’s presidency.

Over many years, North Korea and Iran have both carried out numerous ballistic missile tests, including multiple tests by both countries since the Iran nuclear deal took effect this January. That raises the question of why Iran, having promised not to make nuclear weapons, continues to pour resources into testing ballistic missiles. If not for nuclear weapons, then for what? One obvious question is whether North Korea’s nuclear program might be secretly doubling as a nuclear backshop for Iran.??Cruz, in his letter, raised specific worries about North Korea’s test this September of a powerful new rocket booster, which according to North Korean state media had a thrust of 80 tons — enough power to carry “a heavier, or less-minaturized nuclear warhead to the United States.” That happens to be exactly the same amount of thrust referenced in a Jan. 17 Treasury press release that mentioned the excursions of “Iranian missile technicians,” who “within the past several years” have “traveled to North Korea to work on an 80-ton rocket booster being developed by the North Korean government.”

Cruz asked Treasury Secretary Jack Lew to confirm that the capability of North Korea’s new rocket engine, tested in September, was the same as that of the North Korean rocket on which Iranian technicians had been working in North Korea.

Cruz also had some questions for Secretary of State John Kerry, including “What penalties do you plan to announce against Iran in light of its JCPOA violations?” He also wanted to know, “What is the United States doing to ensure that the $1.7 billion paid to Iran in cash earlier this year is not used to finance nuclear weapons research in North Korea?”

From all these Administration officials, Cruz requested answers no later than Nov. 1. To date, according to his staff, he has received no answers at all.

State and Treasury have not even extended the courtesy of acknowledging the letter. From Clapper’s office, at National Intelligence, came a message in October, saying they had received the letter, and would respond. They have not.

That’s an alarming silence. For years, Obama administration officials have dodged questions about possible Iran-North Korea nuclear teamwork by reciting the talking point that any signs of such cooperation would be cause for serious concern. Now it seems Administration officials are skirting even that customary evasion. Why?

My own queries to State, Treasury and National Intelligence, asking why they had not answered Cruz, ran into the same blank walls. State and Treasury made no response. National Intelligence emailed back on Dec. 6 only to say that they had received Cruz’s letter, and “are working to respond as soon as possible.”

Obama’s administration has racked up a record that suggests silence on Iran-related issues is not a good sign. Back in January, when Obama celebrated a $1.7 billion settlement of an old financial dispute with Iran, a number of lawmakers wrote to the Administration asking for details of this transaction, and whether it was a ransom for Iran’s release of American prisoners.??The Administration took weeks to provide even partial replies, denied paying ransom and omitted entirely the manner in which the $1.7 billion had been dispatched to Iran. It took more than six months for Congress and the press to eke out of the Administration the information that the entire $1.7 billion, converted into European hard currency, had been paid to Iran in stacks of cash — hard to trace and convenient chiefly for illicit purposes — with the first installment of $400 million conveyed, ransom-style, on the same day as the prisoner release, and held in Geneva until the airplane carrying the released American prisoners was on its way out of Iran.

For the Obama administration, invested in the Iran nuclear deal as one of Obama’s signature legacies, there is tremendous temptation to ignore or bury any evidence that Iran is cheating. There is also enormous incentive to downplay another of Obama’s legacies: the dramatic enhancement, since he took office in 2009, of the nuclear arsenal and proficiency of North Korea, now honing its increasingly powerful missiles, beefing up its stockpile of nuclear fuel, and preparing for its sixth nuclear test.

If the silent officials of the Obama administration are confident that there has been no nuclear cooperation between Iran and North Korea, it’s time to put that assessment in writing and send it to Cruz. If, on the other hand, Clapper, Kerry, Lew or Obama himself have any information that points to nuclear collaboration, it’s past time to inform Cruz, the rest of Congress and the American public of the staggering extent of the radioactive debacle they are about to hand off to President-elect Donald Trump, under the heading of Obama’s legacy Iran nuclear deal.

Ms. Rosett is Foreign Policy with the Independent Women’s Forum, and blogs at PJMedia.com.