Merkel to urge caution in Washington as more Russian troops reportedly roll into Ukraine

Meanwhile, Ukraine military spokesman Andrily Lysensko told journalists that "1,500 Russian soldiers and 300 pieces of military equipment, including Grad missile systems, crossed the Ukraine-Russia border on February 7 and 8."

Merkel's message that sending Western weapons to Kiev risks escalating the conflict is likely to get a sympathetic hearing when she meets President Barack Obama later in the day.

But critics of Obama's cautious foreign policy approach are already demanding decisive U.S. action to help Kiev fight the separatists in eastern Ukraine, even if this deepens a standoff with Russian President Vladimir Putin.

Nine Ukrainian troops have been killed in the past 24 hours and seven civilians also died, Kiev said on Monday, with fighting particularly intense around the town of Debaltseve, a major rail and road junction northeast of the city of Donetsk.

At a security conference in Munich over the weekend, Merkel said it was uncertain whether further negotiations would lead to a deal with Putin but argued that all opportunities for a diplomatic solution should be pursued.

Merkel, who with French President Francois Hollande is due to meet Putin on Wednesday, has come under fire from U.S. foreign policy hawks in the Republican-controlled Congress who want defensive weapons sent to the Ukraine army.

"The Ukrainians are being slaughtered and we're sending them blankets and meals," Sen. John McCain said at the Munich conference. "Blankets don't do well against Russian tanks."

But Merkel made clear her opposition to arming Kiev. "I understand the debate but I believe that more weapons will not lead to the progress Ukraine needs. I really doubt that," she said.

A Russian speaker who grew up in East Germany, she has taken the lead in pursuing a diplomatic solution, speaking with Putin by phone dozens of times over the past year and meeting him in Russia, Australia and Italy in recent months.

Last week, Merkel and Hollande met Putin in Moscow and followed this up with a conference call on Sunday also including Ukrainian President Petro Poroshenko. The four are due to meet in Minsk on Wednesday, but so far no breakthrough has emerged in the nearly year-long conflict that has claimed over 5,000 lives.

Moscow warned on Monday that Putin will not be spoken to in the language of ultimatums. Asked about media speculation Merkel had issued him an ultimatum at talks on arranging a summit on Ukraine, Kremlin spokesman Dmitry Peskov told Govorit Moskva radio: "Nobody has ever talked to the president in the tone of an ultimatum - and could not do so even if they wanted to."

OBAMA'S OPTIONS

Obama has to decide whether to supply weapons, impose tougher sanctions on Russia in the hope of forcing Putin to compromise, or throw his full weight behind the revised German-French peace initiative, even though U.S. officials accuse Putin of shredding a prior ceasefire agreement signed in September.

U.S. officials, speaking on condition of anonymity, say he will weigh his options carefully and will not be rushed into a decision. "The timetable is fluid. This is too important to make a snap decision," one official said.

Officials say Obama has recommendations on his desk outlining the pros and cons of supplying Ukraine with lethal arms, such as anti-tank weapons, small arms and ammunition.

Some of his top advisers, including Ashton Carter, his choice for new defense secretary, increasingly favor such an approach. National security adviser Susan Rice said arms supplies were under consideration but signaled caution, and stressed the need to maintain unity with European allies.

Such a step would be taken only "in close consultation and in coordination with our partners, whose unity on this issue with us thus far has been a core element of our strength in responding to Russia's aggression", she said.

In Kiev, military spokesman Vyacheslav Seleznyov said government forces had come under attack from the rebels on about 100 separate occasions in the past 24 hours. As well as the nine dead, 26 troops had been wounded.

In eastern Ukraine, regional police chief Vyacheslav Abroskin said seven civilians had been killed by shelling in Debaltseve and another frontline town of Avdiivka on Sunday.

(Reporting by Andreas Rinke and Aleksandar Vasovic; additinal reporting by Pavel Polityuk, Richard Balmforth, Noah Barkin, Lidia Kelly, Denis Pinchuk, Warren Strobel, Matt Spetalnick and Lesley Wroughton; writing by David Stamp, Editing by Sonya Hepinstall)