The top U.S. military official on Wednesday made the case for growing the base defense budget significantly over the $535 billion spending cap imposed by Congress for fiscal 2015.

While the 2015 budget has not yet been passed by Congress, drafts of the 2016 request are being passed back and forth between the Pentagon and White House, and the final top line number "is still moving," said Joint Chiefs Chairman Gen. Martin Dempsey.

But the one thing the two sides are convinced of is that "we need additional top line [funds] for the emerging new requirements" faced by the US military, he said.

There has been some talk that the Pentagon has suggested budgets as high as $60 billion over the $535 billion spending cap.

When Pentagon leadership began drawing up the budget to fund 2016 earlier this year, Russia had not yet annexed Crimea and invaded Ukraine, the Pentagon was not deploying 3,000 troops back to Iraq and thousands more to West Africa to help fight the Ebola outbreak, and leadership had not yet identified capability gaps in the nation's space and nuclear profiles, Dempsey told an audience at the Defense One summit in Washington.

Dempsey called the redeployment of US troops back to Iraq part of "probably a three- or four-year campaign" while insisting that unlike his three previous deployments to Iraq in 1991 and in the early 2000s, this time the United States would remain in an advisory role — at least for the time being.

He insisted that the Iraqi forces are having some tactical success in driving fighters from the Islamic State group out of places like the oil refinery at Baji and in other areas in Anbar, and in the Kurdish-controlled region in the north.

"The military strategy is Iraq first — not Iraq only — and keep the main thing the main thing," he said. The United States will continue to look for ways to help the resistance fighters in Syria fight the militants, he added.

Iraq takes top billing because unlike in Syria, "there's a credible partner in Iraq" in the form of the national government. In Syria, the situation is chaotic and the US is still struggling to define which resistance groups it can work with.

There is much angst on Capitol Hill when it comes to the warmaking powers the White House insists it has in Iraq and Syria. With the latest continuing resolution to fund the federal government running out on Dec. 11, there is a growing consensus that there's little chance Congress will get much done in that regard before the lame duck session ends on Dec 12.

President Obama promised earlier this month to send new language to the Hill to account for the changes in the mission since the 2001-era authorizations that the administration is relying on were drafted with al Qaida in mind, and not the splinter groups fighting in Iraq and Syria.

Speaking at the same event as Dempsey, Rep. Adam Schiff, D-Calif., said "I am increasingly despairing of the likelihood of taking up an authorization for use of military force [AUMF] in the lame duck."

A member of the House Intelligence Committee, Schiff worried that "in the absence of congressional action there's the danger of the country getting sucked into one conflict after another" as the president pecks away at various threats across the globe without oversight from the Hill.

Sitting alongside Schiff was one of the Senate's most vocal proponents of a new AUMF, Sen. Tim Kaine, D-Va. The senator, who sits on both the influential Armed Services and Foreign Relations committees, complained that "the American people should not accept Congress leaving town on Dec. 11 without saying a mumbling word on this. We have been at war since the 8th of August [in Iraq and Syria] so that will have been four months of what the administration describes as a war against ISIL."

Kaine insisted that any new authorization should be careful to focus on fighting the Islamic State, also called the Islamic State of Iraq and the Levant (ISIL), and not include any language that could be used to support overthrowing the Assad regime in Syria.

"ISIL has declared its intentions to harm Americans," he said. "The government of Assad has not. While the Assad regime is a humanitarian nightmare" it does not threaten the United States, he said.

"That means you make this authorization an authorization that is against ISIL. You don't make it about regime change in Syria."

Still, Schiff thinks there will be a new war authorization passed early in the next year.

"I do think that the president, as a former constitutional scholar, does not want to see his legacy be an unending war and a broad precedent to presidential power."

Email: pmcleary@defensenews.com.