* Leaders likely to pick foreign policy chief
* Key posts like economics commissioner to be decided later
* Ukraine sanctions to be addressed, no tough steps seen
By John O'Donnell and Paul Taylor
BRUSSELS, July 16 (Reuters) - European Union leaders meet on Wednesday to pick the bloc's new foreign policy chief after choosing Jean-Claude Juncker to head the executive European Commission, but it may take some weeks before other top EU jobs are finally carved up.
The nominations, including other Commission posts as well as the president of the European Council of EU leaders, will shape Europe's response to challenges from the crisis in Ukraine to a stagnant economy and Britain's wavering membership of the bloc.
Italian Foreign Minister Federica Mogherini, 41, is front-runner for the foreign policy post, although Poland and Baltic states have misgivings about her suitability, seeing her as inexperienced and too soft on Russia in the Ukraine crisis.
The leaders are also likely to discuss further penalties against Russia for its role in Ukraine, although diplomats cautioned that any such measures were unlikely to extend to full economic sanctions.
With Germany and others reluctant to go further, action may mostly involve extending asset freezes and visa bans to more Ukrainian rebels and Russians deemed responsible for destablising eastern Ukraine.
Polish Foreign Minister Radoslaw Sikorski and Bulgaria's Kristalina Georgieva, the EU commissioner for development, are possible alternatives as foreign policy chief if Mogherini is blocked. Some west Europeans see Oxford-educated Sikorski, a respected strategic thinker, as too belligerent toward Moscow.
While some countries want to finalise the selection in a package deal on Wednesday, officials cautioned that more talks lay ahead over jobs that may include an influential permanent head of the group of euro zone finance ministers.
"I wouldn't expect a package deal," said one official with knowledge of the talks. "I think they will only agree on the high representative (foreign affairs), which is a crucial part of the puzzle. The aim is to finalise by the end of July."
The jobs selection is delicate given the wide disparity of views across the 28 countries in the European Union, an uneasy alliance spanning Britain, where eurosceptics want to quit the bloc, to Greece, which narrowly avoided leaving.
Other key posts at the European Commission, which proposes and enforces laws for 500 million Europeans, include the commissioners in charge of economic affairs, competition, trade, the internal market and energy policy.
Juncker, who won a broad investiture vote in the European Parliament on Tuesday, will attend the summit as president-elect before composing his team in early August from candidates put forward by national governments.
Politics as well as skills and experience will determine his picks, which have to balance gender, party affiliation, small and large countries, and north, south, east and western Europe.
Mogherini, supported strongly by Italian Prime Minister Matteo Renzi, is a Socialist and a woman - factors which may play to her advantage. Juncker is seeking to put more women in top jobs to improve on the current Commission's count of nine.
Britain make face an uphill struggle to secure an important position for its nominee, little known lawmaker Jonathan Hill, who backs Prime Minister David Cameron's strategy of trying to renegotiate London's EU membership terms before a promised 2017 referendum on whether to stay in the bloc.
Cameron, who unsuccessfully fought Juncker's appointment, named more hardline Eurosceptics to his cabinet in a reshuffle on Tuesday, including new foreign minister Philip Hammond. Hill appeared to have been dispatched to Brussels from the House of Lords largely to avoid a parliamentary by-election.
Britain may be able to claim a partial victory if Danish Prime Minister Helle Thorning-Schmidt, 47, a social democrat with good ties to Cameron, became the next president of the European Council, chairing the summit meetings of leaders.
But while she has broad support, France may oppose her appointment because she is not from a euro zone country. (Additional reporting by Adrian Croft; Editing by Paul Taylor and Ralph Boulton)