Oh boy.

PARIS (NYT) — If an agreement to limit Iran’s nuclear capability is reached by deadline in the next seven days, one thing may be missing: an actual written accord, signed by the Iranians.

Over the past few weeks, Iran has increasingly resisted any kind of formal “framework” agreement at this stage in the negotiations, preferring a more general statement of “understanding” followed by a final accord in June, according to Western diplomats involved in the talks.

Should that position hold — one of the many unknowns of the coming days — the United States and its five negotiating partners may find themselves in the uncomfortable position of describing the accord as they understand it while the Iranians go home to offer their own version.

That poses a weighty political challenge to the Obama administration, which is already under pressure to present Iran’s commitments to a suspicious Congress by early April, in an effort to hold off the passage of sanctions or a bill that would require Congress to sign off on any agreement.