LONDON, SEPT. 27 -- Britain and Iran today resumed full diplomatic relations severed by Tehran 18 months ago over the Salman Rushdie affair, bringing the Iranian government closer to the West and kindling new hopes for the release of Western hostages in Lebanon.

Both countries announced that embassies would reopen in their capitals within a month.

Foreign Secretary Douglas Hurd told British reporters at the United Nations in New York that the restoration of ties was "one more brick in building this coalition" against Iraqi President Saddam Hussein, noting that Iran had pledged to enforce international sanctions against Baghdad despite its condemnation of U.S. troop deployment in the Persian Gulf.

Hurd also said the Iranian government had pledged to use its "humanitarian influence" to help obtain the release of the hostages, who include Terry Waite, seized in January 1987 while on a mission for the archbishop of Canterbury to gain the freedom of those already held in Beirut.

But Hurd said Britain had received no firm commitment from Tehran that the hostages would be released, nor that Iran would release British businessman Roger Cooper, held since December 1985 as an alleged spy. Hurd also said the Iranian government had not lifted the death sentence against Rushdie for his authorship of "The Satanic Verses," a novel deemed "blasphemous" to Islam.

"These matters are best settled with the resumption of diplomatic relations," Hurd told BBC Radio.

"There are no undertakings," Hurd added. "It's a matter of judgment on my part whether the chances of getting Roger Cooper out, the chances of getting the hostages out of Lebanon are greater or less now if we restore diplomatic relations. I believe they are greater."

Iran cut off relations in March 1989 after ayatollah Ruhollah Khomeini issued a death order against Rushdie. Since then, Rushdie, a British citizen of Moslem birth, has been in hiding in police custody, and Scotland Yard has uncovered several plots to kill him. Khomeini died in June 1989.

In recent weeks, as the government of President Ali Akbar Hashemi Rafsanjani has sought to improve relations with the West, Iran and Britain have engaged in a diplomatic ballet of mutual public concessions. Rafsanjani made clear that while his government was not authorized to lift the death order, it would "abide by international law," which British diplomats said indicated it would not seek to kill Rushdie.

Hurd, for his part, last month praised Islam as "one of the world's great religions" and emphasized that Britain had no responsibility for the novel's publication.

Frances d'Souza, head of the Rushdie Defense Committee, said she was disappointed that Britain had not insisted that the death order be removed before resuming ties. She said Rushdie, with whom she spoke today, would remain in hiding.

Iran has capitalized diplomatically on the gulf crisis by restoring some of its standing with the West while at the same time wringing major concessions from Iraq. The gulf crisis also has enhanced Rafsanjani's position in Iran's turbulent domestic politics, according to analysts in Tehran. His stand against a traditional foe of Iran won widespread support from factions usually at odds with each other and weakened the power of the hard-line opposition.