LONDON (Reuters) - British Prime Minister Theresa May and U.S. President Donald Trump have said the world must act to ensure those behind a suspected chemical attack in Syria are held to account, as Washington considers a multinational military response.

Britain's Prime Minister Theresa May speaks during a joint news conference with Sweden's Prime Minister Stefan Lofven (not in picture) at Rosenbad, Stockholm, Sweden April 9, 2018. TT News Agency/Jonas Ekstromer/via REUTERS

Trump promised on Monday forceful action in response to the attack that killed at least 60 people and injured more than 1,000, according to a Syrian relief group. U.S. officials said military options were being developed.

May spoke with Trump by telephone on Tuesday afternoon, agreeing that the reported attack was “utterly reprehensible” and that the international community must respond to uphold the worldwide prohibition on chemical weapon use.

“They agreed they would continue working closely together and with international partners to ensure that those responsible were held to account,” a statement from May’s office said.

May had earlier agreed the same thing in a call with French President Emmanuel Macron.

A White House statement said Trump and May “agreed not to allow the use of chemical weapons to continue”.

May, whose Conservatives lack a parliamentary majority, is wary of the domestic political risks of promising military action. So far she has focused on the need to discover the facts about the attack and establish a common international response. But British diplomats have indicated that all options remain on the table.

Britain currently conducts air strikes in Syria from its military base in Cyprus, but only against targets linked to the Islamic State militant group.

Parliament voted down British military action against President Bashar al-Assad’s government in 2013, in an embarrassment for May’s predecessor, David Cameron, that then deterred the U.S. administration of Barack Obama from similar action.

“If the government is proposing to expand its military activity in Syria, they should seek a fresh parliamentary mandate for that action,” a spokeswoman for Britain’s opposition Labour Party said.

Asked by a reporter whether Britain would join the United States if Washington decided on further military action, May said only: “We believe that those responsible should be held to account.”

Some Conservative party members have already urged May to consider committing to a military response without seeking the approval of parliament, which is due to return from recess on April 16.

May is not obliged to win such approval, but a non-binding constitutional convention to do so has been established since a 2003 vote on joining the U.S.-led invasion of Iraq. It has been observed in subsequent military deployments in Libya and Iraq.