US secretary of state Antony Blinken has kicked off his latest Middle East diplomatic mission in Turkey, as fears mount that Israel’s war against Hamas in Gaza may explode into a broader conflict.

Mr Blinken’s fourth visit in three months comes amid worrying developments outside of Gaza, including in Lebanon, northern Israel, the Red Sea and Iraq, that have put intense strains on a US push to prevent a regional conflagration in the weeks after the war began, as well as growing international criticism of Israel’s military operation.

America’s top diplomat met Turkish President Recep Tayyip Erdogan and foreign minister Hakan Fidan to discuss what Turkey and others can do to exert their influence, particularly on Iran and its proxies, to ease soaring tensions, speed up humanitarian aid deliveries to Gaza and begin in earnest to plan for reconstruction and governance of post-war Gaza.

Mr Blinken later stopped in Chania, a port city on the Mediterranean island of Crete, to see Greece’s Prime Minister, Kyriakos Mitsotakis, at his residence.

“These are difficult and challenging times,” Mr Mitsotakis said.

The difficulty of Mr Blinken’s task was underlined just hours before his talks with Mr Erdogan as Lebanon’s Iran-backed Hezbollah militia fired dozens of rockets at northern Israel.

The group warned that the barrage was just an initial response to the targeted killing, presumably by Israel, of a top leader from the allied Hamas group in Lebanon’s capital earlier this week.

Meanwhile, increased attacks on commercial shipping in the Red Sea by Yemen’s Iran-backed Houthi rebels have disrupted international trade and led to increased efforts on the part of the US and its allies to patrol the area and respond to threats, including possibly taking direct action against the group at its bases in Yemen.

The Houthis have carried out at least two dozen attacks in response to the Israel-Hamas war in Gaza just since December 19, which have further heightened tensions and raised risks for the global economy.

In Istanbul, American officials said Mr Blinken would be seeking a Turkish buy-in, or at least consideration of potential monetary or in-kind contributions to reconstruction efforts and some form of participation in a proposed multi-national force that could operate in or adjacent to the territory.

Turkey, and Mr Erdogan in particular, have been harshly critical of Israel and Israeli Prime Minister Benjamin Netanyahu for the prosecution of the war and the impact it has had on Palestinian civilians.

In addition, officials said, Mr Blinken will stress the importance the US places on Turkey ratifying Sweden’s membership of Nato, a long-delayed process that the Turks have said they will complete soon.

Sweden’s accession to the alliance is seen as one critical response to Russia’s invasion of Ukraine.

According to a Turkish official, Mr Fidan told Mr Blinken that Israel’s “increasing aggression” in Gaza was a threat to the region and called for an immediate ceasefire and the delivery of “uninterrupted” humanitarian aid.

The Turkish minister said negotiations for a two-state solution should begin “as soon as possible”.

Mr Fidan also said Turkey was awaiting the outcome of Ankara’s request to upgrade its fleet of F-16 fighter jets and stressed that the ratification of Sweden’s Nato membership lay in the hands of the Turkish parliament.

From Turkey, Mr Blinken travelled to Turkish rival and fellow Nato ally Greece to meet Mr Mitsotakis at his residence on Crete.

Mr Mitsotakis and his government have been supportive of US efforts to prevent the Gaza war from spreading and have signalled their willingness to assist should the situation deteriorate further.

Greece has also shown patience in waiting for the delivery of advanced American fighter jets as the issue of Sweden’s accession to Nato is worked out with Turkey.

Mr Blinken will end his Saturday in Jordan, which apart from Israel has been the secretary’s most frequent stop on his recent Middle East tours.

Jordan will be the first Arab nation on Mr Blinken’s current tour, and will be followed by Qatar, the United Arab Emirates and Saudi Arabia on Sunday and Monday. Mr Blinken will then visit Israel and the West Bank on Tuesday and Wednesday before wrapping up the trip in Egypt.

“We don’t expect every conversation on this trip to be easy,” state department spokesman Matthew Miller said shortly before Mr Blinken departed Washington.

“There are obviously tough issues facing the region and difficult choices ahead. But the secretary believes it is the responsibility of the United States of America to lead diplomatic efforts to tackle those challenges head-on, and he’s prepared to do that in the days to come.”

As well as pressing Israel for dramatic increases in humanitarian aid to Gaza, a shift toward less intense military operations and a concerted effort to rein in violence against Palestinians in the occupied West Bank by Jewish settlers, Mr Blinken will be urging reluctant Gulf Arab nations to work with America on the future of Gaza.