KIEV, Ukraine — President Vladimir V. Putin of Russia waded deep into Ukraine's electoral crisis on Thursday, dismissing the challenger's demand for a repeat of the disputed presidential runoff election and criticizing European efforts to mediate.

Putin made his remarks during a meeting with President Leonid D. Kuchma — who made an unexpected trip to Russia even as Ukrainian lawmakers wrangled over the details of holding new elections and the Supreme Court heard arguments to nullify the results of the vote on Nov. 21, which was tainted by allegations of widespread fraud.

The meeting — at an airport outside Moscow as Putin prepared to fly to India for a state visit — came only hours after Kuchma and his chosen successor, Prime Minister Viktor F. Yanukovich, the nominal winner, had met with the Western-leaning challenger, Viktor A. Yushchenko, and with European diplomats. That meeting, on Wednesday night, yielded several agreements designed to settle the increasingly bitter and tense impasse over the runoff.

The election imbroglio has exposed Russia's desire to maintain its influence over its former czarist and Soviet domains. Putin's direct interference underscores his keen desire to keep Ukraine, in particular, Russia's historical and cultural partner, from tipping toward the West and further diminishing Moscow's reach. The impact of Putin's remarks remains to be seen, but he clearly threw his political prestige behind Kuchma, hardening what emerged on Thursday as starkly divergent positions on how to hold a new vote.

Among the agreements announced Wednesday night was one to swiftly rewrite Ukraine's election law to allow a new vote, assuming the Supreme Court invalidates the results declaring Yanukovich the winner. During a day of backroom negotiations at the parliament — which reportedly included some talks between Yushchenko and Kuchma — Yushchenko reiterated his demand for a new runoff election.

Kuchma, however, insisted on a new election from scratch, throwing open the door for a new pro-government and pro-Moscow candidate other than Yanukovich. Putin backed Kuchma, ridiculing Yushchenko's position.

"A rerun of the second round may also produce nothing," Putin said in remarks broadcast at length on Russia's state television, which also appears in Ukraine. "What happens then? Will there have to be a third, a fourth, a 25th round until one of the sides obtains the necessary result?"

Yushchenko, appearing before thousands of supporters in Independence Square in Kiev, dismissed the idea of a whole new election. "We are not taking part in negotiations if they are about new elections," he declared.