US President Barack Obama flew home from Saudi Arabia on  Saturday under fire for not doing more to raise human rights concerns on a visit dominated by smoothing policy differences with a longtime ally.Obama met a campaigner for the rights of women in the ultra-conservative Muslim kingdom before leaving on Saturday morning.But despite appeals from US lawmakers, he did not raise any rights issues in his talks with King Abdullah late on Friday, which were dominated by policy on Iran and Syria, a source of friction between the allies, a senior US official said.The official insisted that did not mean Obama did not share "significant concerns," merely that the conflict in Syria and Riyadh's concerns about Washington's diplomatic engagement with Tehran had left no time to discuss them."We do have a lot of significant concerns about the human rights situation that have been ongoing with respect to women’s rights, with respect to religious freedom, with respect to free and open dialogue," the official said.But "given the extent of time that they spent on Iran and Syria, they didn’t get to a number of issues and it wasn’t just human rights."Saudi Arabia has strong reservations about efforts by Washington and other major powers to negotiate a deal with Iran on its controversial nuclear programme.The Sunni Muslim oil kingpin, long wary of Shiite Iran's regional ambitions, views a November deal between the powers and Iran aimed at buying time to negotiate a comprehensive accord as a risky venture that could embolden Tehran.Riyadh -- a staunch supporter of the Syrian rebels -- was also deeply disappointed by Obama's 11th-hour decision last year not to take military action against Tehran ally Damascus over chemical weapons attacks.Obama sought to reassure Abdullah on both issues in Friday's meeting, telling the king that the strategic interests of the United States and its longtime ally remained "very much aligned", the US official said.- 'Missed opportunity' -But Obama's focus on smoothing over the strains in the alliance to the exclusion of concerns over women's rights and religious freedoms drew criticism from international watchdogs and from activists inside the kingdom."President Obama's visit offered a crucial opportunity to raise a series of human rights issues from discrimination against women to the repression of independent human rights activists and freedom of expression and assembly," said Amnesty International's Saudi researcher Sevag Kechichian."His failure to publicly voice his concerns over the dire state of human rights in Saudi Arabia is disappointing and a real missed opportunity," Kechichian told AFP.Obama's meeting with Maha Al-Muneef, who was honoured by the US State Department earlier this month for her bravery in campaigning against domestic violence and child abuse, came as activists called for a new day of defiance of the kingdom's unique and deeply controversial ban on women driving.A small number of women responded to the call, the latest in a campaign of defiance launched last October."I drove my car for a while on Olaya Road in Riyadh," activist Aziza Yousef told AFP, adding that she was one of several women who got behind the wheel across the country.Women in Saudi Arabia need permission from their male guardians to travel, marry, work and enrol in higher education.Women who have been stopped by police during previous protests against the driving ban have been required to sign pledges before being released not to do so again.Dozens of US lawmakers had called on Obama to publicly address Saudi Arabia's "systematic human rights violations", including the rights of women.Saudi activist Nasima al-Sada expressed "disappointment" that Obama had met only Muneef and not a wider delegation of women activists. "We were hoping he would meet a delegation of female civil society activists to explain the situation of women and human rights in a better way," she told AFP.She said the meeting with Muneef did "not send a real message of support for the rights of women" in Saudi Arabia.