By Steve Holland, Parisa Hafezi and Ariba Shahid

WASHINGTON/DUBAI/KARACHI, May 18 (Reuters) - U.S. President Donald Trump said on Monday he had paused a planned attack against Iran to allow for negotiations to take place on a deal to end the U.S.-Israeli war, after Iran ‌sent a new peace proposal to Washington.

Trump said he had instructed the U.S. military that "we will NOT be doing the scheduled attack of ‌Iran tomorrow, but have further instructed them to be prepared to go forward with a full, large scale assault of Iran, on a moment’s notice, in the event that an acceptable Deal ​is not reached."

No such attack had previously been announced, and Reuters could not determine whether preparations have been made for strikes that would mark a renewal of the war Trump started in late February.

Under pressure to reach an accord that would reopen the Strait of Hormuz, Trump has previously expressed hope that a deal was close on ending the war, and similarly threatened heavy strikes on Iran if Tehran does not reach a deal.

In his post, he said the leaders of Qatar, Saudi ‌Arabia and the United Arab Emirates had requested that ⁠he hold off on the attack because "a Deal will be made, which will be very acceptable to the United States of America, as well as all Countries in the Middle East, and beyond." He did not offer details of the ⁠agreement being discussed.

Trump's post came after Iranian Foreign Ministry spokesperson Esmaeil Baghaei confirmed that Tehran's views had been "conveyed to the American side through Pakistan" but gave no details.

A Pakistani source confirmed that Islamabad, which has conveyed messages between the sides in the war in the Middle East since hosting the only round of peace talks last month, had ​shared ​the latest proposal with Washington. But the source suggested progress had been difficult.

The sides "keep ​changing their goalposts," the Pakistani source said, adding: "We don't have ‌much time."

PROPOSAL DESCRIBED AS SIMILAR TO PREVIOUS OFFER

The Iranian proposal, as described by a senior Iranian source, appeared similar in many respects to Iran's previous offer, which Trump rejected last week as "garbage".

It would focus first on securing an end to the war, reopening the Strait of Hormuz - a major oil supply route that Iran has effectively blockaded - and lifting maritime sanctions.

Contentious issues around Iran's nuclear programme and uranium enrichment would be deferred to later rounds of talks, the source said.

However, in an apparent softening of Washington's stance, the senior Iranian source said on Monday that the United States had agreed to release a quarter of ‌Iran's frozen funds - totalling tens of billions of dollars - held in foreign banks. Iran wants ​all the assets released.

The Iranian source also said Washington had shown more flexibility in agreeing to ​let Iran continue some peaceful nuclear activity under supervision of the ​International Atomic Energy Agency.

The U.S. has not confirmed that it has agreed to anything in the talks.

Iran's Tasnim news agency ‌separately quoted an unidentified source as saying the U.S. had agreed ​to waive oil sanctions on Iran while ​negotiations were under way.

Iranian officials did not immediately comment on Tasnim's report, which a U.S. official, who declined to be named, said was false.

A fragile ceasefire is in place after six weeks of war that followed U.S.-Israeli airstrikes on Iran, although drones have been launched from Iraq ​towards Gulf countries, including Saudi Arabia and Kuwait, apparently ‌by Iran and its allies. Pakistan's Foreign Ministry issued a statement on Monday condemning a drone attack on Sunday, in which Saudi ​Arabia said it had intercepted three drones that entered the country from Iraqi airspace.

(Reporting by Reuters bureaux; Writing by Timothy Heritage and ​Simon Lewis; Editing by Kevin Liffey, Peter Graff, Deepa Babington and Cynthia Osterman)