Reuters Iran's President Mahmoud Ahmadinejad attends an unveiling ceremony of new nuclear projects in Tehran in this February 15, 2012 file photo

The clock is ticking and the window is closing for a diplomatic solution to the Iran nuclear standoff, Secretary of State Hillary Clinton warned Saturday, ahead of talks scheduled for April 13 in Istanbul. “We are determined to prevent Iran from obtaining a nuclear weapon,” Clinton declared. Speaking of the planned meeting between Iran and the P5+1 group comprising the major Western powers, Russia and China, she added: “We enter into these talks with a sober perspective about Iran’s intentions. It is incumbent upon Iran to demonstrate by its actions that it is a willing partner and to participate in these negotiations with an effort to obtain concrete results.” And, as if to underscore the sense of mounting drama, President Obama last Friday authorized a tightening of sanctions against countries buying oil from Iran.

But just what is closing the Obama Administration’s metaphorical window is not exactly clear: The President made clear earlier this month that he would be willing to take military action if that became necessary to stop Iran acquiring a nuclear weapon, but in the same breath he noted that Iran is not currently building such a weapon, and has taken no decision to do so.

As such, Iran remains on the right side of the “red line” drawn by President Obama for a military strike, even if its steady expansion of its nuclear infrastructure puts put the capacity to make a weapon closer to hand. And Iran is effectively declaring its intent to stay on the right side of Obama’s red line: Both the President and the Secretary of State noted the recent public reiteration by Iran’s Supreme Leader Ayatullah Ali Khamenei of a fatwa that declares nuclear weapons a sin against Islam, and called on Iran to come to the table to negotiate the creation of mechanisms through which Tehran can verify to the world that its nuclear program conforms to Khamenei’s stated edict.

(VIDEO: 10 Questions for Israeli President Shimon Peres)

If the window slams shut at the point that the U.S. decides to take military action, then it would occur only when U.S. intelligence assessed that Iran has made a qualitative shift towards weaponization in its current nuclear work. Meanwhile, Obama would, through a series of coercive disincentives and diplomatic incentives, seek to create conditions that prompt Iran to forgo the option of building nuclear weapons by tightening international scrutiny over its program.

But there are other factors “closing the window”

threats by Israel to take unilateral military action according to its own red lines and timetable;

election-season optics in which the White House may deem it necessary to deny Republican opponents an issue with which to berate the President by hanging tough on Iran; and

a U.S. strategy based on the premise that pressing Iran up against a wall, through imposing an economic stranglehold and danglng a threat of military force, is the key to a diplomatic solution.

While Obama draws the red line at Iran building a nuclear weapon, the Israelis have decried as intolerable the current status quo, in which Iran maintains the technological capacity to build nuclear weapons. That has made it until now opposed to any outcome in which Iran retains the right to enrich uranium on its own soil, even as part of an energy program under international scrutiny. And Defense Minister Ehud Barak has spoken of a timetable based on Iran’s nuclear facilities entering what he calls a “zone of immunity,” in which some of that existing nuclear infrastructure is placed in hardened underground facilities, such as the one at Fordow near Qom, that are beyond the reach of the ordnance available to the Israeli Air Force.

Taking a demonstrably tough line on Iran is also clearly in line with Obama reelection campaign priorities, in order to neutralize the Republican clamor that the President is somehow feckless in the face of a gathering Iran danger. Creating a sense of minutes-to-midnight urgency about the next round of talks certainly demonstrates that the White House is prioritizing the issue over all other foreign policy concerns, and the “last-chance” rhetoric plays to the notion that Iran must fear devastating consequences from its continued defiance if a breakthrough is to be achieved.

MORE: The Ayatullah vs. The President