Prime Minister Boris Johnson has accused Iran of attacks on Saudi Arabian oil facilities ahead of a meeting with the country's president, Hassan Rouhani.
Mr Johnson said there was a "very high level of probability" that Iran was behind the drone and missile attacks at two oil facilities, which Tehran denies.
The Prime Minister refused to rule out military intervention and said sanctions were also a possibility.
The United States, which also blames Iran, sends more troops to Saudi Arabia.
Saudi Arabia has also accused Iran of carrying out the attacks on September 1
Speaking aboard a RAF Voyager jet en route to the United Nations General Assembly in New York, Johnson gave Britain the first responsibility.
He said: "I can tell you that the United Kingdom attributes a very high probability of Iran to Iran for the Aramco attack."
Mr. Johnson said he would cooperate with the United States and other European countries "to construct a responses trying to scale down tensions in the Gulf region. "
Yemen's Iran-aligned Houthi rebels have taken responsibility while Iran itself has denied any involvement. It warned that it would avenge all attacks after the United States announced that they were sending troops to Saudi Arabia.
"Clearly if we were asked either by the Saudis or the Americans to have a role we would consider in what way we could be useful," Johnson said.
On the question of military action was possible, he said: "We will consider how we can be useful if asked and depending on what the exact plan is."
Sanctions also remained on the table, he said.
A Whitehall source said the Houthi rebels' claims of responsibility were "incredible" because the attack's "scope, sophistication and scope" were beyond their capabilities.  The Prime Minister participates in a joint meeting with French President Emmanuel Macron and German Chancellor Angela Merkel at the UN to discuss the attacks, together with Brexit.
Mr. Johnson is also to meet with US President Donald Trump, and the two have discussed the need for a "united diplomatic response".
In his meeting with Mr Rouhani, the Prime Minister said that he would also address the case of Nazanin Zaghari-Ratcliffe and other dual British-Iranian citizens held in Tehran.
Mr. Johnson came under harsh criticism as Foreign Secretary after appearing to contradict Ms. Zaghari-Ratcliffe, who says she was in Iran visiting the family.
She is serving a five-year sentence for spying complaints, which she has always denied.