German Chancellor Angela Merkel will not appear at French President Nicolas Sarkozy's election rallies, but the two are set to meet before the April-May French presidential election, Sarkozy said on Wednesday.

Merkel's Christian Democrat CDU party said in January she would make joint campaign appearances with fellow conservative Sarkozy but the party said this week none had been scheduled, raising questions about whether they would happen at all.

Sarkozy's call on Sunday for tougher controls at Europe's borders sounded alarm bells in Germany even though the president has said he had given Merkel prior notice that he would bring it up in the campaign.

Asked on Europe 1 radio whether he still expected to meet with Merkel ahead of the election, Sarkozy said without doubt at one moment or another.

I don't think at a rally because the election campaign is a French matter between ourselves, but rather to speak about Europe. It's normal that we speak together, he said.

Merkel endorsed Sarkozy during a joint television interview last month, shortly before the president formally announced his re-election bid. The two leaders have worked so closely to overcome the euro zone's debt crisis that they have become known by the joint nickname Merkozy.

But German Foreign Minister Guido Westerwelle, a member of the liberal Free Democratic junior partners in Merkel's coalition, told Reuters on Tuesday that Sarkozy was on the wrong track when he called for tougher controls of Europe's borders. The French leader threatened to pull France out of the EU's Schengen open-border zone unilaterally if he did not get his way.

Sarkozy has also raised eyebrows on the other side of the Rhine by saying on Sunday that Europe needed a version of the United States Buy American Act which would require governments to favour Europe-made products in public procurement.

Jean-François Copé, the leader of Sarkozy's ruling UMP party, told Reuters that as far as he knew there had never been a plan for Merkel to appear at a Sarkozy rally.

This has not been discussed, at least not at my level, he said.

Merkel has refused to meet Sarkozy's Socialist challenger, Francois Hollande, who has been cold-shouldered by most serving European leaders, partly due to a promise to renegotiate a new EU fiscal discipline treaty to include more focus on growth.

Less than six weeks from the election, Sarkozy is struggling to catch up with Hollande in opinion polls although one survey on Tuesday put him ahead of his Socialist adversary for the first time in the first round. The poll showed Hollande winning comfortably on the second round.