US Secretary of State John Kerry and Saudi Foreign Minister Adel al-Jubeir insisted Thursday that their countries' ties remain strong despite recent tensions over Washington's outreach to Iran.

The top envoys met in London for talks on a variety of Middle East issues, including the wars in Syria and Yemen and the imminent implementation of the Iran nuclear deal.

Washington has used the deal, under which Tehran agreed to limit its nuclear ambitions in exchange for a softening on sanctions, as a springboard to seek more productive ties with its old foe.

But at the same time Riyadh's relations with Iran, long hostile, have plunged to new lows. Saudi Arabia cut off diplomatic contact with Tehran last week after an Iranian mob ransacked its embassy there.

Saudi Arabia has regarded Kerry's cautious outreach to Tehran -- and burgeoning relationship with its Foreign minister Mohammad Javad Zarif -- with suspicion, and the London visit was designed to rebuild trust.

‘We agree, first of all, the alliance, the friendship between the United States and the kingdom of Saudi Arabia remains a lynchpin of our efforts in the region. It's important. We both agree with that, on both sides,’ Kerry told reporters as he welcomed al-Jubeir.

Without mentioning Iran, Kerry expressed sympathy for Saudi Arabia's concerns -- shared by the United States -- over its web of influence in the Arab world.

‘We also understand the challenges that the kingdom and other countries feel in the region about interference in their countries,’ he said.

‘We want to try to see if there's a way, moving forward, to resolve some of these problems without moving to greater conflict. The last thing the region needs is more conflict,’ he continued.

‘And I know the kingdom of Saudi Arabia agrees with that. But there are simple things they would like to see done that help prevent that.’

The United States expressed concern after Saudi Arabia marked the New Year by carrying out a mass execution, including that of a respected Shia cleric accused of fomenting sedition.

Sheikh Nimr al-Nimr's death triggered outrage in Iran, and the protest led to the sacking of the Saudi embassy, an act Riyadh blamed on Tehran.

Al-Jubeir responded: ‘I think if you look at the challenges our region faces, whether in Syria, whether in Yemen, whether terrorists, whether in Iran's interference in the affairs of the region, or Libya, the most effective ways for us to work though these challenges is through our close partnership and alliance with the United States of America.’

The pair's meeting was to continue.