President Hamid Karzai's startling threat to join the Taliban if foreigners don't stop meddling in Afghanistan and his strident criticism of the West's role have worsened relations with Washington at a time when the US military wants closer cooperation ahead of a potentially decisive offensive this summer. Karzai has been fuming for months about what he considers Washington's heavy hand. He's gambling that blaming outsiders for the troubles in a society with a long tradition of resisting occupation will bolster his stature at home – while carrying little risk because the US has no choice but to deal with him. But managing the rift has now become a major problem for both sides, threatening even to rival the threat from the Taliban. President Barack Obama's strategy depends on working with a strong, reliable Afghan partner to turn back a resurgent Taliban, raising the question of what will happen if that partnership fails. Karzai's comments suggest that his understanding of partnership differs from Obama's considerably. On certain issues, Karzai clearly wants Washington to back off. “Troubling” is how White House spokesman Robert Gibbs described reports Monday that Karzai threatened to abandon the political process and join the Taliban insurgency if the West keeps carping at him to reform his government. “On behalf of the American people, we're frustrated with the remarks,” Gibbs told reporters. “These comments can undercut the kind of support that we think we need on all sides of this equation if we're going to move forward,” State Department spokesman P.J. Crowley said. “Clearly, you know, what he says does have an impact back here in the United States and he should choose his words carefully.” Karzai has long chaffed under what he considers excessive international pressure. Those complaints escalated Thursday when he lashed out against the UN and the international community, accusing them of perpetrating a “vast fraud” in last year's presidential polls as part of a conspiracy to deny him re-election or tarnish his victory – accusations the US and the United Nations have denied. Two days later, Karzai told a group of parliament members that if foreign interference in his government continues, the Taliban would become a legitimate resistance – one that he might even join, according to several lawmakers present. “He said that ‘if I come under foreign pressure, I might join the Taliban,”' said Farooq Marenai, who represents the eastern province of Nangarhar. “He said rebellion” against a legitimate Afghan government “would change to resistance” against foreign occupation. Two other parliament members gave the same account but asked that their names not be published to avoid problems with Karzai. Calls to two Karzai spokesmen went unanswered because their mobile phones were shut off. Karzai told CNN on Monday that he has no intention of breaking with Washington, which is pouring 30,000 more troops into the fight against the Taliban. “It's just to make sure that we all understand as to where each one of us stands,” Karzai said. “Afghanistan is the home of Afghans and we own this place. And our partners are here to help in a cause that's all of us. We run this country, the Afghans.” The lawmakers agreed that the threat to join the Taliban did not appear serious but reflected Karzai's anger over US and international pressure on several issues, including electoral reform, combating corruption and contacts with Taliban insurgents. Those differences were sharpened by Obama's unannounced visit to Kabul on March 28. In advance of the trip, Obama's national security adviser, James Jones, told reporters that Karzai needed once and for all to confront corruption and “be seized with how important that is.” Karzai's advisers found the public tongue-lashing humiliating – especially coming from a guest. At the same time, the US and its partners have been urging Karzai to reform the electoral system to avoid the corruption that marked the Aug. 20 presidential balloting, when a third of the president's votes were thrown out by a UN-backed anti-fraud watchdog. That forced him under US pressure to accept an embarrassing runoff, which was called off when his remaining challenger complained that the second election would be no cleaner than the first. The US and its partners want changes in place by September, when Afghans choose a new parliament. Karzai associates have said the president considers Western complaints of corruption a smoke screen to discredit his government and draw attention from the fact that most of the billions in international aid have been squandered by the donors themselves and not wasted by his government. Last February, Karzai issued a presidential decree taking control of the anti-fraud body and removing UN-appointed foreigners from any watchdog role. Karzai's outbursts over the past week came after the parliament overturned the decree, a move the president believed was in response to international pressure.