Prime Minister David Cameron secured the support of Poland's most powerful man on Friday, February 5, for a proposed deal to keep Britain in the European Union, Reuters reports.
Opinion poll suggested, however, voters may still reject continued membership in a planned referendum.
To win a vote expected in June on staying in the EU, Cameron says he needs a pact to curb benefits for new migrant workers from EU countries, an opt-out from moves towards political union, more powers for national parliaments and safeguards to ensure Britain is not put at a disadvantage by being one of nine EU members outside the euro currency zone.
He achieved an important step towards that goal when Jaroslaw Kaczynski, leader of Poland's ruling Law and Justice party and the country's top decision maker, gave his blessing to the proposed arrangements for new migrant workers.
Also, Cameron received Denmark's backing for the deal, according to BBC News.
Danish PM Lars Lokke Rasmussen said plans for a brake on benefit payments were "understandable and acceptable" and he would be as "supportive as possible" to keep the UK in the EU.
Negotiators from all 28 EU countries meanwhile held a first discussion in Brussels of the package put forward by European Council President Donald Tusk. Diplomats said the day-long meeting was broadly supportive and threw up no roadblocks.
The so-called sherpas will meet again on February 11 with the aim of reaching a deal at a Feb. 18-19 EU summit.
After meeting with Cameron in Warsaw, Kaczynski said he was satisfied because the rights of some 600,000 Poles already working in the UK would be fully preserved.
"We have gained really very, very much," said Kaczynski, who is also a former prime minister and the twin brother of late president Lech Kaczynski.