WASHINGTON (AP) — Vast differences between Iran and the six-nation coalition seeking to dismantle the Islamic republic’s nuclear program may lead to another short-term deal — and that could renew criticism that Iran is stalling and energize the push in Congress for tougher sanctions even if they endanger negotiations.

Such a dilemma awaits the resumption of face-to-face talks set for next month. The six-month agreement achieved last November went into effect on Monday. The deal froze key parts of Iran’s nuclear program in exchange for easing some trade and financial penalties.