* Agreement struck in June has swiftly unravelled

* Both sides accuse each other of failing to stick to terms

* Strait of Hormuz remains closed

* Attacks on shipping on Tuesday rattled markets again

By Parisa Hafezi and Elwely Elwelly

DUBAI, Aug 12 (Reuters) - Iran and the United States remain

at loggerheads over efforts to agree a permanent end to the war

in the Gulf, according to a senior Iranian source who said there

had been no progress in talks to revive the interim deal agreed

in June and define a timeframe to implement it.

The comments were a further blow to hopes of a swift

resolution to the crisis, following attacks on shipping in the

region on Tuesday that pushed oil prices higher.

The deal agreed in June declared an "immediate and permanent

termination of military operations on all fronts", but quickly

unravelled, with U.S. President Donald Trump saying it was

"over" on July 7 and Iran's foreign ministry declaring it

"suspended" a week later.

The U.S. accuses Iran of failing to honour an agreement

under the deal to reopen the vital Strait of Hormuz shipping

route. Tehran says Washington has reneged on its commitments,

including lifting a blockade of Iranian ports and releasing

frozen Iranian assets.

"One of the issues that is being discussed via mediators is

the U.S. returning to the interim agreement and defining a

timeframe for implementing the commitments. There has been

absolutely no progress on this issue," the Iranian source said.

There was no immediate comment from Washington.

Thousands of people have been killed in the conflict, mainly

in Iran and Lebanon, since the U.S. and Israel launched attacks

on Iran on February 28.

Iran has struck U.S. assets and infrastructure in countries

including Oman, Jordan, Kuwait, Israel, the United Arab Emirates

and Saudi Arabia.

BOTH SIDES STEP UP RHETORIC

The June interim ceasefire agreement set a 60-day period,

extendable by mutual consent, within which Iran and the U.S.

were expected to reach a final deal limiting Tehran's nuclear

programme and lifting U.S. sanctions.

The Iranian source dismissed a report on Wednesday from

Turkey's Anadolu news agency that quoted Pakistani government

sources as saying they had agreed to extend that 60-day period.

"There is no talk of an extension because, from Iran's

perspective, there is no period that began and therefore nothing

to extend. The United States violated the interim agreement 48

hours after it was reached and withdrew from it a few days

later," the source told Reuters.

Both Iran and the United States have stepped up rhetoric in

the past two days.

Iran's top security official, Mohsen Rezaei, said on Tuesday

that the Strait of Hormuz would remain closed unless the U.S.

accepted Iran's conditions to end the war.

That followed a new demand from Trump on Monday that Iran

should pay compensation for people killed in 50 years of wars,

attacks and protests.

Throughout the conflict, Trump has alternated between

threats of escalation and claims that a peace deal is imminent.

Speaking to reporters after a visit to Ohio on Tuesday,

Trump said: "Iran is going fine, going just absolutely fine."

"We have a country that has been the bully of the Middle

East for 50 years, really 51 if you think about it ... and

they're no longer the bully of the Middle East."

ATTACKS ON SHIPPING

The Strait of Hormuz, a narrow waterway between Iran and

Oman and the entrance to the Gulf, handled a fifth of global oil

and liquefied natural gas flow before the war.

Benchmark Brent crude futures have surged since the

start of the war in February, hitting a peak of $126 a barrel,

roughly 75% above pre-war levels, with choppy trade reflecting

concerns over disruptions to Gulf oil supplies and shifting

signals on peace talks.

Those concerns were compounded by separate attacks on

shipping on Tuesday.

At the southern end of the Red Sea, four crew members were

killed in an attack by Iran-backed Houthis on a small cargo ship

in the Bab el-Mandeb Strait on Tuesday, the first deadly strike

on shipping by the group since the start of the war.

The U.S. military, meanwhile, said a U.S. Navy MH-60

helicopter fired two Hellfire missiles to disable the steering

gear of a Panama-flagged cargo ship.

The ship ignored repeated warnings to stop violating a naval

blockade on Iranian ports, the U.S. Central Command said.

Maritime sources told Reuters the vessel was hit off Pakistan

while sailing into the Gulf of Oman.

Brent futures rose 35 cents, or 0.4%, to $89.26 a barrel on

Wednesday, heading for a sixth day of gains.