The nuclear agreement between Western powers and Iran was broadly welcomed by politicians, former world leaders and Middle East experts.
As Sergei Lavrov and John Kerry bid for a peaceful resolution to Syria, a former British diplomat says the US is "taking on the master".
Is Russia's proposal for international monitors to oversee Syria's arsenal of chemical weapons, serious diplomacy or just making trouble?
US Secretary of State John Kerry has sought offer assurances to Israel over the Iran nuclear deal, saying that the agreement would make Israel safer over the next six months.
Kerry told CNN's State of the Union: "Israel is threatened by what has been going on in Iran.
"But I believe that from this day - for the next six months - Israel is in fact safer than it was yesterday, because we now have a mechanism by which we are going to expand the amount of time in which they [Iran] can break out [toward creating a nuclear bomb].
"We are going to have insights to their program that we didn't have before".
Foreign Secretary William Hague has returned to London for a meeting with US Secretary of State John Kerry on the Middle East.
Mr Hague wrote on Twitter:
US Secretary of State John Kerry has arrived in the UK ahead of his meeting with Foreign Secretary William Hague on the Middle East peace process.
Mr Hague and Mr Kerry are also expected to discuss the latest developments in Syria and Libya.
Foreign Secretary William Hague and US Secretary of State John Kerry will have talks in London tomorrow on the Middle East, the State Department has said.
As well as further discussions on Iran, they are expected to consider the latest developments in Syria and the Middle East peace process.
Libyan officials will also be present at the meeting, the State Department added.
US Secretary of State John Kerry has arrived in Geneva ahead of high-level talks on Iran's nuclear programme.
A State Department press officer tweeted this photo of him arriving at the airport:
US Secretary of State John Kerry will travel to Israel on Friday to discuss a proposed deal with Iran on the country's nuclear programme, Israeli Prime Minister Benjamin Netanyahu has said.
Mr Netanyahu has condemned a proposal, endorsed by Washington, to reduce sanctions on Iran if Tehran suspends parts of its nuclear work.
The Israeli prime minister said he would discuss the issue with French President Francois Hollande, who arrives in Israel later today, and with Russian President Vladimir Putin when he visits Moscow on Wednesday.
US Secretary of State John Kerry will visit Geneva to join nuclear negotiations with Iran and other major powers, the Associated Press reported, citing official sources.
Kerry's last-minute decision to join the talks suggests a deal could be imminent.
He will participate in the talks after a brief stop in Israel, where he will hold a third meeting with Israeli Prime Minister Benjamin Netanyahu.
US Secretary of State John Kerry has called for stability in Egypt during his first visit to the country since President Mohammed Morsi was ousted in July.
Speaking at a news conference, he said: "All of Egypt's future will be defined not only by the way the road map is implemented and the way the constitution is formed but by the economic choices and opportunities that are created over there next weeks and months.
He also stressed the need for fair and transparent trials for all Egyptians.
Kerry's visit comes the day before Morsi and 14 other senior Muslim Brotherhood leaders are due to go on trial charged with inciting violence.
John Kerry said the US's relationship with Egypt is "very important" as he visited the country for the first time since former president Mohamed Morsi was ousted.
The US Secretary of State said he had discussed with Egypt's foreign minister the need to end violence and have a constitution that "protects the interests of all all Egyptians".