Slovakia's prime minister says his country is challenging a European Union decision to redistribute 120,000 asylum seekers.
Robert Fico says Slovakia is not ready to accept the plan to share the burden of migrants across the EU.
"We won't implement this decision because we think it can't work," he told reporters ahead of a meeting of EU leaders in Brussels.
Slovakia opposed the plan along with the Czech Republic, Romania and Hungary.
Mr Fico described the quota system as "irrational" and says his country "is not ready to respect it. We always rejected it as nonsense".
Czech Prime Minister Bohuslav Sobotka said he will not take legal action against the plan.
In an email message, Mr Sobotka said: "Even though I don't like the use of the quotas, I don't agree with them and we voted against them, Europe must not fall apart over solving the migrant crisis."
He continued: "That's why I don't want to escalate the tension by challenge it with legal actions. There are more battles ahead of us over a realistic approach to the migrant crisis and we need our partners in Europe to listen to our arguments."
Romania's president says his country can cope with the extra migrants the European Union wants it to receive, but disagrees with the way the matter was decided.
President Klaus Iohannis said Romania would be asked to take around 2,400 extra on top of the 1,785 already agreed.
Mr Iohannis said "it is an unusual and inopportune thing that a vote was forced", but added that "Romania is not against refugees, or receiving refugees".
He said quotas "take into account the realities of every state".
European Union leaders have been called to an emergency summit to seek long-term responses to the crisis.
In a letter to presidents and prime ministers of member states, EU President Donald Tusk wrote: "There is a long list of issues where we could blame one another, but it will not help us in finding a common solution."
He added: "Today we must absolutely work out policies that we can implement in order to help each other."
Slovakian media used strong words to express bitter feelings after the plan was approved.
A headline in business daily Hospodarske Noviny, said: "The Germans won a blitzkrieg."
The daily Pravda's front page said: "Slovakia suffered a loss in its fight against the quotas."
Meanwhile, around 2,500 migrants and refugees have arrived at the main border point between Austria and Hungary, a day after 5,000 crossed into Austria.
An Austrian police spokesman said the new arrivals were transported to the Hungarian side of the Nickelsdorf crossing point early on Wednesday. They are walking into Austria from there.