US President Donald Trump has issued a new threat to Tehran, tweeting that a conflict would be the "official end" of Iran, as Saudi Arabia warned it stood ready to respond with "all strength" and it was up to Iran to avoid war.
The heightened rhetoric follows last week's attacks on Saudi oil assets and the firing of a rocket on Sunday into Baghdad's heavily fortified Green Zone that exploded near the US embassy.
"If Iran wants to fight, that will be the official end of Iran. Never threaten the United States again!" Trump said in a tweet without elaborating.
A US State Department official said the rocket attack in Baghdad did not hit a US-inhabited facility and produced no casualties nor any significant damage. No claims of responsibility had been made, but the US was taking the incident "very seriously."
Riyadh, while emphasising that it does not want a war, has accused Tehran of ordering Tuesday's drone strikes on two oil pumping stations in the kingdom, claimed by Yemen's Iran-aligned Houthi group.
Two days earlier, four vessels, including two Saudi oil tankers, were sabotaged off the coast of the United Arab Emirates.
Iran has denied involvement in either incident, which come as Washington and the Islamic Republic spar over sanctions and the US military presence in the region, raising concerns about a potential US-Iran conflict.
"The kingdom of Saudi Arabia does not want a war in the region nor does it seek that," Minister of State for Foreign Affairs Adel al-Jubeir said on Sunday.
Saudi Arabia's King Salman on Sunday invited Gulf and Arab leaders to convene emergency summits in Mecca on May 30 to discuss implications of the attacks.
Saudi Arabia and Shi'ite Iran are arch-adversaries in the Middle East, backing opposite sides in several regional wars.
The US Navy's Fifth Fleet said in a statement that GCC countries were "specifically increasing communication and coordination with each other in support of regional naval cooperation and maritime security operations in the Arabian Gulf," with navies and coast guards working with the US Navy.
Saudi Arabia's ally the UAE has not blamed anyone for the tanker sabotage operation, pending an investigation. No-one has claimed responsibility, but two US government sources said last week that US officials believed Iran had encouraged the Houthi group or Iraq-based Shi'ite militias to carry it out.
The drone strike on oil pumping stations, which Riyadh said did not disrupt output or exports, was claimed by the Houthis, who have been battling a Saudi-led military coalition in a war in Yemen since 2015.
Iranian Foreign Minister Mohammad Javad Zarif has dismissed the possibility of war erupting, saying Tehran did not want conflict and no country had the "illusion it can confront Iran".
This stance was echoed by the head of Iran's elite Revolutionary Guards, Major General Hossein Salami.
Washington has tightened economic sanctions against Iran, trying to cut Tehran's oil exports to zero, and beefed up the US military presence in the Gulf in response to what it said were Iranian threats to US troops and interests.
Australian Associated Press