DUBAI, Sept 2 (Reuters) - Iran has sent a "constructive" response to U.S. proposals aimed at reviving Tehran's 2015 nuclear deal with world powers, Iran's Foreign Ministry said, prompting a less positive impression from the United States.

"The text that was sent (by Iran) has a constructive approach aimed at finalizing the negotiations," Foreign Ministry spokesperson Nasser Kanaani was quoted as saying by state broadcaster IRIB on Friday.

But the U.S. State Department gave a different assessment.

"We can confirm that we have received Iran's response through the EU," a spokesperson said. "We are studying it and will respond through the EU, but unfortunately it is not constructive."

White House National Security Council spokesperson Adrienne Watson said: "Some gaps have closed in recent weeks but others remain."

The IRIB report said Iran's response was sent to EU foreign policy chief Josep Borrell, who has been coordinating the negotiations. It gave no further details.

After 16 months of indirect talks between Tehran and Washington, Borrell said on Aug. 8 the EU had laid down a final offer to overcome an impasse for the revival of the agreement.

Iran needs stronger guarantees from Washington for the revival of a 2015 nuclear deal, its foreign minister said on Wednesday, adding that the U.N. atomic watchdog should drop its "politically motivated probes" of Tehran's nuclear work.

Under the 2015 pact, Iran had curbed its nuclear program in return for relief from U.S., EU and U.N. sanctions.

Then U.S. President Donald Trump reneged on the deal in 2018, arguing that it was too generous to Tehran. He reimposed U.S. sanctions on Iran, leading Tehran to resume previously banned nuclear activities and reviving U.S., European and Israeli fears that Iran may seek an atomic bomb.

Iran denies any such ambition.