May and Jordan's King Abdullah II flew by helicopter to a military base on the outskirts of the capital of Amman where they greeted troops and inspected weaponry.
"It is clearly in the UK's security and prosperity interests to support Jordan and Saudi Arabia in tackling regional challenges to create a more stable region, and in delivering their ambitious reform programmes to ensure their own stability".
May also said she would continue to raise the issue of women's rights in Saudi Arabia, suggesting they would be able to look to her for inspiration.
May has come under harsh criticism over her Saudi visit, facing calls at home to raise rights issues with local leaders.
The British government said May will emphasize her country's close partnership with Saudi Arabia, including on counterterrorism cooperation. Jordan has carried out air strikes against IS targets as part of a US -led military coalition against IS.
"She would not put up with it in the United Kingdom, so why in the Middle East?"
With Britain looking to strike new trade deals as it prepares to leave the EU, May has eyed longtime partners in the energy-rich Gulf states.
Qatar announced plans last month to invest pound 5 billion ($6.23 billion/5.8 billion euros) in Britain within five years.
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Britain has continued to allow arms sales, with more than £3 billion of exports since the bombing began in March 2015.
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As part of her visit, Mrs May is also setting out details of how a £1bn package to support victims of the fighting in Syria will be spent.
Hundreds of those airstrikes have targeted schools, hospitals, wedding parties and funerals where hundreds of civilians were killed in what aid groups, including the United Nations, have said could amount to war crimes. Additionally, some 21 million Yemenis, roughly 82 percent of the population, are in urgent need of humanitarian assistance.
Her comments come after her visit was strongly criticised by Labour leader Jeremy Corbyn on Monday on account of the Saudi Arabia's human rights record and its military actions in Yemen.
"The Foreign Secretary expressed his regret at the disturbance to Saudi Major General Asseri's visit to London on Thursday", the Foreign Office said.
An anti-war activist last week attempted a citizen's arrest of Assiri, before another threw an egg that hit the spokesman in the back. May said she'll discuss the conflict and resulting humanitarian conflict in Yemen with Saudi leaders, pointing out that Britain was the fourth-biggest donor of humanitarian aid to Yemen past year, channeling 103 million pounds to the country.
Saudi Arabia is not a signatory of the convention agreed by over 100 signatories in 2010.