WASHINGTON — The Senate is taking up the massive 2017 defense policy this week, as Senate Armed Services Chairman John McCain is expected to ask Congress to authorize $17 billion above spending caps.

When the $602 billion 2017 National Defense Authorization Act hits the Senate floor this week, McCain plans introduce the added funding through an amendment. Pass or fail, this stand-alone vote on defense spending would be a tough one for Democratic lawmakers who have demanded that each defense dollar be matched in domestic spending.

"I don't know whether or not this amendment will succeed, but the Senate must have this debate and senators must choose a side," McCain, R-Ariz., said at a May 19 event at Brookings' Center for 21st Century Security and Intelligence.

A preview of the spending debate is contained in McCain's May 20 "dear colleague" letter, in which he pressed for more F-35 Joint Strike Fighters and Army helicopters, as well as more F-18 fighter jets and accelerated shipbuilding on the Virginia-class submarine and Raleigh Burke destroyer. He is also seeking more money to support local forces fighting the Islamic State group and Taliban respectively. He also favors halting planned drawdowns for the Army and Marine Corps.

McCain acknowledged the 2015 budget deal as a "necessary compromise" but said the president's budget funds defense at $17 billion less than Defense Department leaders planned in their five-year plan — and argued the military services are left "underfunded, undersized, and unready to meet current and future threats."

The House, in attempting to raise the authorization for defense spending but not alter the defense top-line break in the 2015 budget deal, passed a version of the 2017 NDAA that uses $23 billion in wartime funding to pay for base budget needs. Lawmakers had added $18 billion for base budget requirements, such as jets, ships and troops cut by the administration and salvaged from the military services' "unfunded priorities" lists.

The House version also cuts off wartime overseas contingency operations (OCO) funding after April 30, 2017, a gambit to force the next president to ask Congress for supplemental defense spending next year. The House Appropriations Committee last week approved a defense spending bill that takes a similar approach.

McCain signaled weeks ago that he planned to take a different approach, while the White House has issued a threat to veto such legislation, and Defense Secretary Ash Carter and Democratic leadership have condemned the House plan.

Potentially, McCain's request for more defense spending could rally Democrats to ask for more non-defense spending — a prospect that would awaken the ire of fiscal hawks, particularly House Republicans.

"My instinct that Sen. McCain's amendment would just be about increasing defense spending in the NDAA, and that kind of dollar-for-dollar increase on other issues wouldn't be germane there, so you have a vote for the first time, in recent memory at least, on whether we should increase defense spending or not, without the ancillary issues," said Justin Johnson, a senior defense policy analyst at The Heritage Foundation.

Despite the divergent funding approaches in the House and Senate, if McCain is successful in his floor amendment to increase the top-line for defense, it is not likely to be a major issue as lawmakers in the House and Senate reconcile the differences in their bills in conference over the coming weeks, said Mackenzie Eaglen, an American Enterprise Institute analyst and former congressional defense aide.

That is because the Senate version of the bill uses the House bill's plus-ups — based on the unfunded priorities list — as a blueprint for where they will apply additional dollars, with a special emphasis on procurement as well, Eaglen said. The issue would then be that the House version's top-line may need to increase because SASC would've fully funded OCO.

Johnson said that while there is potentially a fundamental budget disconnect between the House and Senate that would have to be worked out, the added money, if the amendment passes, would make it "a big veto target." That thorny question could delay a final bill into law until after the election, leaving a cloud of uncertainty over major Pentagon acquisition programs and policy decisions.

"The trickle down effects of that, just in terms of Army force structure, Marine force structure, how many ships you're going to buy, F-18s you're going to buy, any of the stuff where you have big differences can be worked out until you know what your budget approach is going to be," Johnson said.

Twitter: @ReporterJoe