"They need to stop lying, come back to reason and accept that we will all find a place for Catalonia within Spain", he said before travelling to Washington, where Prime Minister Mariano Rajoy is due to meet US President Donald Trump.
President Trump said Tuesday that the United States opposes an independence drive in the Spanish region of Catalonia, telling reporters that such secession would be "foolish".
Spain's central government and regional Catalan authorities argued this weekend over who controls the regional police force that is considered key to the success of a planned independence vote for the north-eastern region.
They are cracking down on organisers by threatening them with prosecution.
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The three ministers also voiced their "strong commitment" to maintain Iraq's territorial and political unity. The country has the largest Kurdish population in the region and is already battling a Kurdish insurgency.
Eighteen MSPs expressed "grave concern" at the actions of the Spanish state in a letter to Spain's prime minister.
The government has in recent weeks taken political and legal measures to prevent the referendum by exerting more control over the use of public funds in Catalonia, arresting regional officials and seizing election leaflets.
If Catalonia favours a split, the pressure on Madrid to allow an official vote will grow, according to analysts.
Police also went to the office of Oliana Mayor Miguel Sala, one of 700 mayors under investigation for saying they would cooperate with the referendum.
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Campos said her parents brought her to the United States from Mexico before her first birthday. As she was escorted out, Pelosi said: "They don't want the DREAM Act ".
This has sparked protests in Barcelona and other cities.
"These articles have been violated by the order sent to Spanish telecommunications operators to cut access to web pages that inform about the referendum on self-determination, as well as those internet domains that are publicized or published to the social networks of the. members of the Government", the Catalan government complains in the letter.
A "yes" vote is likely, given that most of the 40 percent of Catalans who polls show support independence are expected to cast ballots while most of those against it are not.
But the unrelenting opposition from Madrid means such a result would go all but unrecognized, potentially setting up a new phase of the dispute.
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Shares in Tata Steel rose 2% on news of the deal in Mumbai, while those in ThyssenKrupp opened 5% higher in Frankfurt. Under the agreement, both the companies will have 50% stake in the newly formed entity.
Trump also offered prayers and support to those affected by deadly attacks last month that killed 16 people in Barcelona and a nearby town. "They are excluding half the population", Dastis said.