Bahrain has told a senior US diplomat who met representatives of the country's opposition that he is "unwelcome" in the kingdom and should "leave immediately".
The foreign ministry accused US assistant secretary of state for democracy, human rights and labour Tom Malinowski, of meddling in Bahrain's internal affairs, in a statement published by the official BNA state news agency.
The ministry said Malinowski met "with a particular party to the detriment of other interlocutors", an apparent reference to the Shiite-led opposition in Sunni-ruled Bahrain.
It added that Malinowski "is unwelcome and should immediately leave the country, due to his interference in its internal affairs".
State Department spokeswoman Jen Psaki said on Monday that Malinowski was still in Bahrain. "He is on a visit to reaffirm and strengthen our bilateral ties and to support his royal majesty King Hamad's reform and reconciliation efforts at an important time, particularly given events elsewhere in the region," she said.
Psaki said Malinowski's visit "had been coordinated far in advance and warmly welcomed and encouraged by the government of Bahrain, which is well aware that US government officials routinely meet with all officially recognised political societies.
"Contrary to our long-standing bilateral relationship and in violation of international diplomatic protocol, the government insisted - without advance warning and after his visit had already commenced - to have a Foreign Ministry representative present at all of assistant secretary Malinowski's private meetings with individuals and groups representing a broad spectrum of Bahraini society, including those held at the US embassy".
Psaki added: "These actions are not consistent with the strong partnership between the United States and Bahrain."
Malinowski met leaders of the opposition, including cleric Ali Salman, the head of the main Shiite opposition movement Al-Wefaq, which is an authorised political association, according to the group.
Shiite-led protests erupted in Bahrain - home base of the US Fifth Fleet - in February 2011, taking their cue from uprisings elsewhere in the region and demanding democratic reforms in the absolute monarchy.
Security forces boosted by Saudi-led troops ended the protests a month later, but smaller demonstrations frequently take place in Shiite villages, triggering clashes with police.
The United States has been repeatedly criticised by rights group for not taking a strong stance on Bahrain's crackdown on protests. The opposition has campaigned for the establishment of a genuine constitutional monarchy in Bahrain.