Iran's foreign minister said on Sunday it was too early to talk of reopening the U.S. Embassy in Tehran, as Britain restored its diplomatic mission four years after protesters ransacked the British ambassador's residence.

British Foreign Secretary Philip Hammond attended a ceremony at the opulent 19th century building in the Iranian capital where attackers in 2011 burned Britain's national flag, slashed portraits of British monarchs and stole goods.

Iran's Foreign Minister Javad Zarif, asked if Tehran would now countenance a restoration of the US diplomatic mission, said the United States' "illogical attitude" towards Iran meant the time was not ripe for a similar move with Washington.

"It seems that there needs to be a change in that kind of attitude and behaviour on the part of the U.S. So the situation is different with the U.S.," he said.

The U.S. embassy was sacked in the early days of the Islamic Revolution in 1979 by students who feared a repeat of a 1953 coup, when the CIA orchestrated the overthrow of Iran's prime minister. The ensuing U.S. hostage crisis lasted 444 days and Washington and Tehran have yet to restore diplomatic ties.

Iran reopened its embassy in London on Sunday in a reciprocal move that followed a deal on Iran's disputed nuclear programme reached last month with six major world powers, including Britain and the United States.

U.S. President Barack Obama has promised to exercise his veto if the U.S. Congress, dominated by Republicans opposed to the deal, rejects the agreement, which would start the process of lifting a raft of sanctions which have hurt Iran's economy.