By Laurence Norman and Matthew Dalton 

BRUSSELS--Europe is coalescing behind a plan to impose wider economic sanctions on Russia as early as Tuesday, European Union officials said Friday.

The movement came after a meeting of ambassadors from EU member states to discuss ratcheting up pressure on Moscow because of what the West says is its support for pro-Russia rebels in eastern Ukraine.

Herman Van Rompuy, president of the European Council, sent a letter to EU leaders saying the ambassadors had found "emerging consensus" on a plan to restrict Russian access to European capital markets, and an embargo on trade in weapons as well as exports of militarily sensitive goods and energy-sector technology to Russia. A copy of the letter was seen by The Wall Street Journal.

The trade embargo won't affect existing contracts, the letter says. That is important for France, which doesn't want to cancel the planned delivery of a Mistral warship to Russia scheduled for the fall. Some Eastern European nations also worried they could lose access to parts needed to maintain Soviet-era military equipment.

An export ban on goods with dual civilian-military use will apply only to Russian military customers at first, the letter adds. Restrictions on energy technology will apply only to oil-industry equipment, since the EU depends in particular on Russian natural gas, the letter says.

"My assessment is that this package strikes the right balance," Mr. Van Rompuy wrote. "It should have a strong impact on Russia's economy while keeping a moderate effect on EU economies."

The expected move to hit the Russian economy with tougher measures follows the shooting down of a Malaysia Airlines jet over eastern Ukraine, allegedly by Russia-backed separatists, with more than 200 EU citizens among the dead.

Late Friday, the European Commission, the EU's executive, said it had formally adopted proposed legislation for detailing the sanctions, which will now go to member states for review.

"The final decision now lies with the EU's member states but I believe that this is an effective, well-targeted and balanced package providing the flexibility to adjust our reaction to changes on the ground," said commission President José Manuel Barroso.

Mr. Van Rompuy asked the leaders to direct ambassadors to approve the sanctions when they meet on Tuesday, avoiding the need for another high-level summit. The European Council represents member state governments in Brussels.

The EU on Thursday agreed to add 18 entities to its sanctions list, including the separatist groups People's Republic of Luhansk and Donetsk People's Republic and some Crimea-based companies that benefited from the Russian annexation of the region, diplomats said.

Also targeted were 15 individuals, including the chief of the Federal Security Service, the KGB's successor agency, EU diplomats said.

EU officials said their names were to be published late Friday in the bloc's official journal, after which the visa ban and asset freeze takes immediate effect. However, the publication was delayed because of technical reasons, officials said.

The EU also agreed Thursday to clear the way for sanctions on people they determine to be actively supporting Russian decision makers on actions in Ukraine, including the annexation of Crimea in March. That could include Russian oligarchs close to the Kremlin and more of Russian President Vladimir Putin's senior advisers and aides.

People familiar with the discussions said the ambassadors wanted to focus Friday's discussions on the broader economic sanctions before opening a fresh debate over who else to target among Mr. Putin's inner circle. However Mr. Van Rompuy said in his letter the additional targeted sanctions would be ready for adoption by Monday.

One of the issues that governments will need to address is how to scale up or down the sanctions as the situation in Ukraine changes. The draft legal decisions won't set out any detailed conditions, officials said, leaving such delicate political decisions as they arise to member states.

The proposals for economic sanctions, described in a document distributed to member states and seen by the Journal on Thursday, include investment restrictions and a prohibition on listing Russian financial instruments on European markets or exchanges--measures that could hit Sberbank, Russia's largest bank and one of the biggest in Europe.

Russian financial institutions that are more than 50%-owned by the Russian government would also be subject to the restrictions, the document says. Those financial institutions raised EUR7.5 billion ($10 billion) in bonds from EU capital markets in 2013, 47% of all the bonds they issued, the document says. EU citizens would be forbidden from buying their equity or debt with a maturity longer than 90 days.

Write to Laurence Norman at laurence.norman@wsj.com and Matthew Dalton at Matthew.Dalton@wsj.com