An uptick in clashes between Iranian security forces and Kurdish rebel groups is threatening to open a new front in the Islamic Republic's conflict with the United States and Israel, testing a fragile ceasefire between Tehran and Washington.

Iran’s joint military command warned Thursday that all oil tankers moving through the Strait of Hormuz must use its approved routes or face a “forceful response,” again ratcheting up tensions over a waterway crucial for international energy supplies.

Senior U.S. officials have said Iran would be richly rewarded for changing its stance on the United States. Iran’s leaders have rejected such a bargain in the past.

A series of strikes over the weekend saw the US and Iran accuse each other of violating the ceasefire agreement.

By Andrew Mills and Elwely Elwelly DOHA/DUBAI, June 30 (Reuters) - Iran said on Tuesday it would not meet with top U.S. envoys who flew to the region following an outbreak of hostilities, clouding the prospects for a lasting peace between the two countries.

The U.S. president is set on bringing gas prices down and reaching a nuclear deal, but Iran has little incentive to cede its newfound power to control shipping traffic.

Chief foreign correspondent Trey Yingst reports as U.S. and Iran talks progress, with President Donald Trump considering military options to prevent Iran from acquiring nuclear weapons.

By Andrew Mills, Parisa Hafezi and Bo Erickson DOHA/DUBAI/WASHINGTON, June 29 (Reuters) - Iranian and U.S. negotiating teams were due in Doha this week, but Iran said on Monday no meeting had been scheduled as weekend missile fire from both sides tested the interim ceasefire to end the four-month-old war.

Iranian state television claimed this week that a foreign ship got stuck in the Strait of Hormuz after ignoring instructions to use a route laid out by the Islamic Republic's paramilitary Revolutionary Guard.