The U.S.-Iran standoff deepened Tuesday as Washington declared a blockade of Iranian ports, Tehran threatened strikes across the region, while Pakistan said it was scrambling to bring both sides back to the negotiating table.

Though last week's cease-fire appeared to hold, the showdown over the Strait of Hormuz risked reigniting hostilities and deepening the region-wide war's economic fallout.

Talks aimed at permanently ending the conflict – which began Feb. 28 with U.S. and Israeli strikes on Iran – failed to produce an agreement last weekend, though Pakistan has proposed hosting a second round in the coming days.

Two Pakistani officials, who spoke on condition of anonymity because they weren't authorized to discuss the matter with the media, said that the first talks were part of an ongoing diplomatic process rather than a one-off effort.

Two U.S. officials, who spoke on the condition of anonymity to discuss sensitive diplomatic negotiations, said Monday that discussions were still underway about a new round of talks. They said that the venue, timing and composition of the delegations hadn't been decided, but that talks could happen Thursday.